Mist inhaler devices

ABSTRACT

A mist inhaler device ( 200 ) for generating a mist including a therapeutic for inhalation by a user. The device includes a mist generator device ( 201 ) and a driver device ( 202 ). The driver device ( 202 ) is configured to drive the mist generator device ( 201 ) at an optimum frequency to maximise the efficiency of mist generation by the mist generator device ( 201 ).

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation of co-pending U.S. applicationSer. No. 17/552,281, filed Dec. 15, 2021, which claims the benefit ofpriority to and incorporates by reference herein the entirety of all thefollowing applications:

U.S. application Ser. No. 17/122,025 filed on 15 Dec. 2020 which claimsthe benefit of priority to International patent application no.PCT/IB2019/060808, filed on 15 Dec. 2019, International patentapplication no. PCT/IB2019/060810, filed on 15 Dec. 2019, Internationalpatent application no. PCT/IB2019/060811, filed on 15 Dec. 2019,International patent application no. PCT/IB2019/060812, filed on 15 Dec.2019, European patent application no. 20168245.7, filed on 6 Apr. 2020,European patent application no. 20168231.7, filed on 6 Apr. 2020, andEuropean patent application no. 20168938.7, filed on 9 Apr. 2020; and

U.S. application Ser. No. 17/220,189 filed on 1 Apr. 2021 which claimsthe benefit of priority to European Patent Application No. 20168231.7,filed on 6 Apr. 2020, all of the foregoing applications are incorporatedherein by reference in their entirety.

FIELD

The present invention relates to mist inhaler devices. The presentinvention more particularly relates to ultrasonic mist inhaler devicesfor atomising a liquid comprising a therapeutic for inhalation by auser.

BACKGROUND

Mist inhaler devices are used for generating a mist or vapour forinhalation by a user. The mist may contain a therapeutic, drug ormedicine which is inhaled by a user and absorbed into the user's bloodstream.

Therapeutic aerosol delivery is the mainstay for the treatment ofasthma, chronic obstructive pulmonary disease (COPD) and cysticfibrosis. Therapeutic aerosol also has applications for the treatment ofinfluenza, osteoporosis as well as the delivery of vaccines.

Pulmonary delivery of therapeutics for the treatment of non-respiratorysystemic disease is appealing because of high lung vascularity, a thinblood-alveolar barrier, large surface area, avoidance of gastric enzymesand first-pass hepatic metabolism. It is also appealing because ofimproved patient comfort and adherence. The pulmonary system can beleveraged to deliver antibodies, proteins, pain killers and nucleicacids. The treatment of central nervous system disorders, such astobacco dependence, could be significantly enhanced through theefficient delivery of nicotine to the systematic circulation through thelungs.

The effectiveness of therapeutic aerosol relates to the amount of drugdeposited beyond the oropharyngeal region. The region where the depositoccurs is a function of the inhaled particles size.

The devices currently used for the administration of inhaled drugs aredivided into three categories: nebulizers, metered-dose inhalers, anddry powder inhalers. Nebulizers are typically divided into two types:jet and ultrasonic but in conventional devices both types haveweaknesses and present issues.

Jet nebulizers are based on the Bernoulli principle and producerelatively large droplets that generally deposit in the oropharyngealregion and are therefore not particularly effective. Ultrasonicnebulizers use piezoelectric crystals that vibrate at frequencies,ranging between 1 MHz and 1.7 MHz, transmitting the vibratory energy tothe liquid converting it to aerosol. It is acknowledged that ultrasonicnebulizers are not effective if viscous suspensions or solutions areused and tend to heat the medication, hence destroy the molecules andremove the benefits of inhalation.

Thus, a need exists in the art for improved mist inhaler devices whichseek to address at least some of the problems described herein.

SUMMARY

The present invention provides a mist inhaler device as claimed in claim1. The present invention also provides preferred embodiments as claimedin the dependent claims.

The various examples of this disclosure which are described below havemultiple benefits and advantages over conventional mist inhaler devices.These benefits and advantages are set out in the description below.

Since the mist inhaler device of examples of this disclosure enableshigher efficiency operation than conventional mist inhaler devices, themist inhaler devices of examples of this disclosure have anenvironmental benefit due to the reduced power requirement.

According to one aspect, there is provided a mist inhaler device forgenerating a mist for inhalation by a user, the device comprising:

-   -   a mist generator device which incorporates:        -   a mist generator housing which is elongate and comprises an            air inlet port and a mist outlet port;        -   a liquid chamber provided within the mist generator housing,            the liquid chamber for containing a liquid to be atomised;        -   a sonication chamber provided within the mist generator            housing;        -   a capillary element extending between the liquid chamber and            the sonication chamber such that a first portion of the            capillary element is within the liquid chamber and a second            portion of the capillary element is within the sonication            chamber;        -   an ultrasonic transducer having a generally planar            atomisation surface which is provided within the sonication            chamber, the ultrasonic transducer being mounted within the            mist generator housing such that the plane of the            atomisation surface is substantially parallel with a            longitudinal length of the mist generator housing, wherein            part of the second portion of the capillary element is            superimposed on part of the atomisation surface, and wherein            the ultrasonic transducer is configured to vibrate the            atomisation surface to atomise a liquid carried by the            second portion of the capillary element to generate a mist            comprising the atomised liquid and air within the sonication            chamber; and        -   an airflow arrangement which provides an air flow path            between the air inlet port, the sonication chamber and the            air outlet port such that a user drawing on the mist outlet            port draws air through the inlet port, through the            sonication chamber and out through the mist outlet port,            with the mist generated in the sonication chamber being            carried by the air out through the mist outlet port for            inhalation by the user, wherein the mist inhaler device            further comprises:    -   a driver device which incorporates:        -   a battery;        -   an AC driver for converting a voltage from the battery into            an AC drive signal at a predetermined frequency to drive the            ultrasonic transducer;        -   an active power monitoring arrangement for monitoring the            active power used by the ultrasonic transducer when the            ultrasonic transducer is driven by the AC drive signal,            wherein the active power monitoring arrangement provides a            monitoring signal which is indicative of an active power            used by the ultrasonic transducer;        -   a processor for controlling the AC driver and for receiving            the monitoring signal drive from the active power monitoring            arrangement; and        -   a memory storing instructions which, when executed by the            processor, cause the processor to:    -   A. control the AC driver to output an AC drive signal to the        ultrasonic transducer at a predetermined sweep frequency;    -   B. calculate the active power being used by the ultrasonic        transducer based on the monitoring signal;    -   C. control the AC driver to modulate the AC drive signal to        maximise the active power being used by the ultrasonic        transducer;    -   D. store a record in the memory of the maximum active power used        by the ultrasonic transducer and the sweep frequency of the AC        drive signal;    -   E. repeat steps A-D for a predetermined number of iterations        with the sweep frequency incrementing or decrementing with each        iteration such that, after the predetermined number of        iterations has occurred, the sweep frequency has been        incremented or decremented from a start sweep frequency to an        end sweep frequency;    -   F. identify from the records stored in the memory the optimum        frequency for the AC drive signal which is the sweep frequency        of the AC drive signal at which a maximum active power is used        by the ultrasonic transducer; and    -   G. control the AC driver to output an AC drive signal to the        ultrasonic transducer at the optimum frequency to drive the        ultrasonic transducer to atomise a liquid.

In some examples, the driver device is releasably attached to the mistgenerator device such that the driver device is separable from the mistgenerator device.

According to another aspect, there is provided a mist generator devicewhich incorporates:

-   -   a mist generator housing which is elongate and comprises an air        inlet port and a mist outlet port;    -   a liquid chamber provided within the mist generator housing, the        liquid chamber for containing a liquid to be atomised;    -   a sonication chamber provided within the mist generator housing;    -   a capillary element extending between the liquid chamber and the        sonication chamber such that a first portion of the capillary        element is within the liquid chamber and a second portion of the        capillary element is within the sonication chamber;    -   an ultrasonic transducer having a generally planar atomisation        surface which is provided within the sonication chamber, the        ultrasonic transducer being mounted within the mist generator        housing such that the plane of the atomisation surface is        substantially parallel with a longitudinal length of the mist        generator housing, wherein part of the second portion of the        capillary element is superimposed on part of the atomisation        surface, and wherein the ultrasonic transducer is configured to        vibrate the atomisation surface to atomise a liquid carried by        the second portion of the capillary element to generate a mist        comprising the atomised liquid and air within the sonication        chamber; and    -   an airflow arrangement which provides an air flow path between        the air inlet port, the sonication chamber and the air outlet        port such that a user drawing on the mist outlet port draws air        through the inlet port, through the sonication chamber and out        through the mist outlet port, with the mist generated in the        sonication chamber being carried by the air out through the mist        outlet port for inhalation by the user.

In some examples, the mist generator device further comprises: atransducer holder which is held within the mist generator housing, thetransducer element holds the ultrasonic transducer and retains thesecond portion of the capillary element superimposed on part of theatomisation surface; and a divider portion which provides a barrierbetween the liquid chamber and the sonication chamber, wherein thedivider portion comprises a capillary aperture through which part of thefirst portion of the capillary element extends.

In some examples, the transducer holder is of liquid silicone rubber.

In some examples, the liquid silicone rubber has a Shore A 60 hardness.

In some examples, the capillary aperture is an elongate slot having awidth of 0.2 mm to 0.4 mm.

In some examples, the capillary element is generally planar with firstportion having a generally rectangular shape and the second portionhaving a partly circular in shape.

In some examples, the capillary element has a thickness of substantially0.28 mm.

In some examples, the capillary element comprises a first part and asecond part which are superimposed on one another such that thecapillary element has two layers.

In some examples, the capillary element is of at least 75% bamboo fibre.

In some examples, the capillary element is 100% bamboo fibre.

In some examples, the airflow arrangement is configured to change thedirection of a flow of air along the air flow path such that the flow ofair is substantially perpendicular to the atomisation surface of theultrasonic transducer as the flow of air passes into the sonicationchamber.

In some examples, the change of direction of the flow of air issubstantially 90°.

In some examples, the airflow arrangement provides an air flow pathhaving an average cross-sectional area of substantially 11.5 mm².

In some examples, the mist generator device further comprises: at leastone absorbent element which is provided adjacent the mist outlet port toabsorb liquid at the mist outlet port.

In some examples, each absorbent element is of bamboo fibre.

In some examples, the mist generator housing is at least partly of aheterophasic copolymer.

In some examples, the heterophasic copolymer is polypropylene.

In some examples, the ultrasonic transducer is circular and has adiameter of substantially 16 mm.

In some examples, the liquid chamber contains a liquid having akinematic viscosity between 1.05 Pa·s and 1.412 Pa·s and a liquiddensity between 1.1 g/ml and 1.3 g/ml.

In some examples, the liquid chamber contains a liquid comprising anicotine levulinate salt at a 1:1 molar ratio.

In some examples, the mist generator device further comprises: anidentification arrangement which is provided on the mist generatorhousing, the identification arrangement comprising: an integratedcircuit having a memory which stores a unique identifier for the mistgenerator device; and an electrical connection which provides anelectronic interface for communication with the integrated circuit.

In some examples, the memory of the integrated circuit stores a recordof the state of the mist generator device which is indicative of atleast one of the historic use of the mist generator device or the volumeof a liquid within the liquid chamber.

According to one aspect, there is provided a driver device for a mistinhaler device, the device comprising:

-   -   a battery;    -   an AC driver for converting a voltage from the battery into an        AC drive signal at a predetermined frequency to drive an        ultrasonic transducer;    -   an active power monitoring arrangement for monitoring the active        power used by the ultrasonic transducer when the ultrasonic        transducer is driven by the AC drive signal, wherein the active        power monitoring arrangement provides a monitoring signal which        is indicative of an active power used by the ultrasonic        transducer;    -   a processor for controlling the AC driver and for receiving the        monitoring signal drive from the active power monitoring        arrangement; and    -   a memory storing instructions which, when executed by the        processor, cause the processor to:    -   A. control the AC driver to output an AC drive signal to the        ultrasonic transducer at a predetermined sweep frequency;    -   B. calculate the active power being used by the ultrasonic        transducer based on the monitoring signal;    -   C. control the AC driver to modulate the AC drive signal to        maximise the active power being used by the ultrasonic        transducer;    -   D. store a record in the memory of the maximum active power used        by the ultrasonic transducer and the sweep frequency of the AC        drive signal;    -   E. repeat steps A-D for a predetermined number of iterations        with the sweep frequency incrementing or decrementing with each        iteration such that, after the predetermined number of        iterations has occurred, the sweep frequency has been        incremented or decremented from a start sweep frequency to an        end sweep frequency;    -   F. identify from the records stored in the memory the optimum        frequency for the AC drive signal which is the sweep frequency        of the AC drive signal at which a maximum active power is used        by the ultrasonic transducer; and    -   G. control the AC driver to output an AC drive signal to the        ultrasonic transducer at the optimum frequency to drive the        ultrasonic transducer to atomise a liquid.

In some examples, the active power monitoring arrangement comprises: acurrent sensing arrangement for sensing a drive current of the AC drivesignal driving the ultrasonic transducer, wherein the active powermonitoring arrangement provides a monitoring signal which is indicativeof the sensed drive current.

In some examples, the current sensing arrangement comprises: anAnalog-to-Digital Converter which converts the sensed drive current intoa digital signal for processing by the processor.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D with the sweepfrequency being incremented from a start sweep frequency of 2900 kHz toan end sweep frequency of 2960 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D with the sweepfrequency being incremented from a start sweep frequency of 2900 kHz toan end sweep frequency of 3100 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: in step G, control the AC driverto output an AC drive signal to the ultrasonic transducer at frequencywhich is shifted by a predetermined shift amount from the optimumfrequency.

In some examples, the predetermined shift amount is between 1-10% of theoptimum frequency.

In some examples, the battery is a 3.7V DC Li—Po battery.

In some examples, the driver device further comprises: a pressure sensorfor sensing a flow of air along a driver device flow path which extendsthrough the driver device.

In some examples, the driver device further comprises: a wirelesscommunication system which is in communication with the processor, thewireless communication system being configured to transmit and receivedata between the driver device and a computing device.

In some examples, the driver device further comprises: a driver devicehousing which is at least partly of metal, wherein the driver devicehousing houses the battery, the processor, the memory, the active powermonitoring arrangement and the AC driver, and wherein the driver devicehousing comprises a recess for receiving and retaining part of the mistgenerator device.

In some examples, the AC driver modulates the AC drive signal by pulsewidth modulation to maximise the active power being used by theultrasonic transducer.

It is noted that the expression “mist” used in the following disclosuremeans the liquid is not heated as usually in traditional inhalers knownfrom the prior art. In fact, traditional inhalers use heating elementsto heat the liquid above its boiling temperature to produce a vapour,which is different from a mist.

In fact, when sonicating liquids at high intensities, the sound wavesthat propagate into the liquid media result in alternating high-pressure(compression) and low-pressure (rarefaction) cycles, at different ratesdepending on the frequency. During the low-pressure cycle,high-intensity ultrasonic waves create small vacuum bubbles or voids inthe liquid. When the bubbles attain a volume at which they can no longerabsorb energy, they collapse violently during a high-pressure cycle.This phenomenon is termed cavitation. During the implosion, very highpressures are reached locally. At cavitation, broken capillary waves aregenerated, and tiny droplets break the surface tension of the liquid andare quickly released into the air, taking mist form.

The following will explain more precisely the cavitation phenomenon.

When the liquid is atomised by ultrasonic vibrations, micro waterbubbles are produced in the liquid.

The bubble production is a process of formation of cavities created bythe negative pressure generated by intense ultrasonic waves generated bythe means of ultrasonic vibrations.

High intensity ultrasonic sound waves leading to rapid growth ofcavities with relatively low and negligible reduction in cavity sizeduring the positive pressure cycle.

Ultrasound waves, like all sound waves, consist of cycles of compressionand expansion. When in contact with a liquid, Compression cycles exert apositive pressure on the liquid, pushing the molecules together.Expansion cycles exert a negative pressure, pulling the molecules awayfrom another.

Intense ultrasound waves create regions of positive pressure andnegative pressure. A cavity can form and grow during the episodes ofnegative pressure. When the cavity attains a critical size, the cavityimplodes.

The amount of negative pressure needed depends on the type and purity ofthe liquid. For truly pure liquids, tensile strengths are so great thatavailable ultrasound generators cannot produce enough negative pressureto make cavities. In pure water, for instance, more than 1,000atmospheres of negative pressure would be required, yet the mostpowerful ultrasound generators produce only about 50 atmospheres ofnegative pressure. The tensile strength of liquids is reduced by the gastrapped within the crevices of the liquid particles. The effect isanalogous to the reduction in strength that occurs from cracks in solidmaterials. When a crevice filled with gas is exposed to anegative-pressure cycle from a sound wave, the reduced pressure makesthe gas in the crevice expand until a small bubble is released intosolution.

However, a bubble irradiated with ultrasound continually absorbs energyfrom alternating compression and expansion cycles of the sound wave.These cause the bubbles to grow and contract, striking a dynamic balancebetween the void inside the bubble and the liquid outside. In somecases, ultrasonic waves will sustain a bubble that simply oscillates insize. In other cases, the average size of the bubble will increase.

Cavity growth depends on the intensity of sound. High-intensityultrasound can expand the cavity so rapidly during the negative-pressurecycle that the cavity never has a chance to shrink during thepositive-pressure cycle. In this process, cavities can grow rapidly inthe course of a single cycle of sound.

For low-intensity ultrasound the size of the cavity oscillates in phasewith the expansion and compression cycles. The surface of a cavityproduced by low-intensity ultrasound is slightly greater duringexpansion cycles than during compression cycles. Since the amount of gasthat diffuses in or out of the cavity depends on the surface area,diffusion into the cavity during expansion cycles will be slightlygreater than diffusion out during compression cycles. For each cycle ofsound, then, the cavity expands a little more than it shrinks. Over manycycles the cavities will grow slowly.

It has been noticed that the growing cavity can eventually reach acritical size where it will most efficiently absorb energy from theultrasound. The critical size depends on the frequency of the ultrasoundwave. Once a cavity has experienced a very rapid growth caused by highintensity ultrasound, it can no longer absorb energy as efficiently fromthe sound waves. Without this energy input the cavity can no longersustain itself. The liquid rushes in and the cavity implodes due to anon-linear response.

The energy released from the implosion causes the liquid to befragmented into microscopic particles which are dispersed into the airas mist.

The equation for description of the above non-linear response phenomenonmay be described by the “Rayleigh-Plesset” equation. This equation canbe derived from the “Navier-Stokes” equation used in fluid dynamics.

The inventors approach was to rewrite the “Rayleigh-Plesset” equation inwhich the bubble volume, V, is used as the dynamic parameter and wherethe physics describing the dissipation is identical to that used in themore classical form where the radius is the dynamic parameter.

The equation used derived as follows:

${{ \frac{❘{\frac{1}{c^{2}}\frac{\delta^{2}\phi}{\delta t^{2}}}❘}{\nabla^{2}\phi} \sim( \frac{R}{\lambda} )^{2}} \ll 1}{{\frac{1}{4\pi}( \frac{4\pi}{3V} )^{\frac{1}{3}}( {\overset{¨}{V} - \frac{{\overset{.}{V}}^{2}(t)}{6V}} )} = {\frac{1}{\rho_{0}}( {{( {p_{0} + {2{\sigma( \frac{4\pi}{3V_{0}} )}^{\frac{1}{3}}} - {pv}} )( \frac{V_{0}}{V} )^{\kappa}} + p_{V} - {2{\sigma( \frac{4\pi}{3V_{0}} )}^{\frac{1}{3}}} - p_{0} - {P(t)}} )}}$

wherein:

V is the bubble volume

V₀ is the equilibrium bubble volume

ρ₀ is the liquid density (assumed to be constant)

σ is the surface tension

p_(v) is the vapour pressure

p₀ is the static pressure in the liquid just outside the bubble wall

κ is the polytropic index of the gas

t is the time

R(t) is the bubble radius

P(t) is the applied pressure

c is the speed sound of the liquid

ϕ is the velocity potential

λ is the wavelength of the insonifying field

In the ultrasonic mist inhaler, the liquid has a kinematic viscositybetween 1.05 Pa·sec and 1.412 Pa·sec.

By solving the above equation with the right parameters of viscosity,density and having a desired target bubble volume of liquid spray intothe air, it has been found that the frequency range of 2.8 MHz to 3.2MHz for liquid viscosity range of 1.05 Pa·s and 1.412 Pa·s produce abubble volume of about 0.25 to 0.5 microns.

The process of ultrasonic cavitation has a significant impact on thenicotine concentration in the produced mist.

No heating elements are involved, thereby leading to no burnt elementsand reducing second-hand smoke effects.

In some examples, said liquid comprises 57-70% (w/w) vegetable glycerineand 30-43% (w/w) propylene glycol, said propylene glycol includingnicotine and optionally flavourings.

In the ultrasonic mist inhaler, a capillary element may extend betweenthe sonication chamber and the liquid chamber.

In the ultrasonic mist inhaler, the capillary element is a material atleast partly in bamboo fibres.

The capillary element allows a high absorption capacity, a high rate ofabsorption as well as a high fluid-retention ratio.

It was found that the inherent properties of the proposed material usedfor the capillarity have a significant impact on the efficientfunctioning of the ultrasonic mist inhaler.

Further, inherent properties of the proposed material include a goodhygroscopicity while maintaining a good permeability. This allows thedrawn liquid to efficiently permeate the capillary while the observedhigh absorption capacity allows the retention of a considerable amountof liquid thus allowing the ultrasonic mist inhaler to last for a longertime when compared with the other products available in the market.

Another significant advantage of using the bamboo fibres is thenaturally occurring antimicrobial bio-agent namely “Kun” inherentlypresent within the bamboo fibre making it antibacterial, anti-fungal andodour resistant, making it suitable for medical applications.

The inherent properties have been verified using numerical analysisregarding the benefits of the bamboo fibre for sonication.

The following formulae have been tested with bamboo fibres material andothers material such cotton, paper, or other fibre strands for the useas capillary element and demonstrates that bamboo fibres have muchbetter properties for the use in sonication:

$C = {A + \frac{T}{W_{f}} - \frac{1}{P_{f}} + {( {1 - \alpha} )\frac{V_{d}}{W_{f}}}}$

wherein:

C (cc/gm of fluid/gm) is the volume per mass of the liquid absorbeddivided by the dry mass of the capillary element,

A (cm²) is the total surface area of the capillary element

T (cm) is the thickness of the capillary element,

W_(f) (gm) is the mass of the dry capillary element,

P_(f) (cc/g·sec) is the density of the dry capillary element,

α is the ratio of increase in volume of capillary element upon wettingto the volume of liquid diffused in the capillary element,

V_(d) (cc) is the amount of liquid diffused in the capillary element,

${{Absorbent}{Rate}},{Q = {\frac{\pi r{\gamma 1}\cos\theta}{2\eta} \cdot ( {\frac{T}{W_{f}} - \frac{1}{AP_{f}}} )}}$

Q (cc/sec) is the amount of liquid absorbed per unit time,

r (cm) is the radius of the pores within the capillary element,

γ (N/m) is the surface tension of the liquid,

θ (degrees) is the angle of contact of the fibre,

η (m²/sec) is the viscosity of the fluid.

In the ultrasonic mist inhaler, the capillary element may be a materialat least partly in bamboo fibres.

In the ultrasonic mist inhaler, the capillary element material may be100% bamboo fibre.

Extensive testing has concluded that a 100% pure bamboo fibre is themost optimal choice for sonication.

In the ultrasonic mist inhaler, the capillary element material may be atleast 75% bamboo fibre and, optionally, 25% cotton.

Capillary element from 100% pure bamboo fibre or with a high percentageof bamboo fibres demonstrates a high absorption capacity as well asimproved fluid transmission making it an optimal choice for theapplication of the ultrasonic mist inhaler.

In the ultrasonic mist inhaler, the capillary element may have a flatshape.

In the ultrasonic mist inhaler, the capillary element may comprise acentral portion and a peripheral portion.

In the ultrasonic mist inhaler, the peripheral portion may have anL-shape cross section extending down to the liquid chamber.

In the ultrasonic mist inhaler, the central portion may have a U-shapecross section extending down to the sonication chamber.

The ultrasonic mist inhaler according to one example, wherein saidliquid to be received in the liquid chamber comprises 57-70% (w/w)vegetable glycerin and 30-43% (w/w) propylene glycol, said propyleneglycol including nicotine and flavourings.

An ultrasonic mist inhaler or a personal ultrasonic atomiser device,comprising:

-   -   a liquid reservoir structure comprising a liquid chamber or        cartridge adapted to receive liquid to be atomised,    -   a sonication chamber in fluid communication with the liquid        chamber or cartridge, wherein said liquid to be received in the        liquid chamber comprises 57-70% (w/w) vegetable glycerin and        30-43% (w/w) propylene glycol, said propylene glycol including        nicotine and flavourings.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the present invention may be more readily understood,embodiments of the present invention will now be described, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 is an exploded view of components of an ultrasonic mist inhaler.

FIG. 2 is an exploded view of components of an inhaler liquid reservoirstructure.

FIG. 3 is a cross section view of components of an inhaler liquidreservoir structure.

FIG. 4A is an isometric view of an airflow member of the inhaler liquidreservoir structure according to FIGS. 2 and 3 .

FIG. 4B is a cross section view of the airflow member shown in FIG. 4A.

FIG. 5 is schematic diagram showing a piezoelectric transducer modelledas an RLC circuit.

FIG. 6 is graph of frequency versus log impedance of an RLC circuit.

FIG. 7 is graph of frequency versus log impedance showing inductive andcapacitive regions of operation of a piezoelectric transducer.

FIG. 8 is flow diagram showing the operation of a frequency controller.

FIG. 9 is a diagrammatic perspective view of a mist inhaler device ofthis disclosure.

FIG. 10 is a diagrammatic perspective view of a mist inhaler device ofthis disclosure.

FIG. 11 is a diagrammatic perspective view of a mist generator device ofthis disclosure.

FIG. 12 is a diagrammatic perspective view of a mist generator device ofthis disclosure.

FIG. 13 is a diagrammatic exploded perspective view of a mist generatordevice of this disclosure.

FIG. 14 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 15 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 16 is a diagrammatic perspective view of a capillary element ofthis disclosure.

FIG. 17 is a diagrammatic perspective view of a capillary element ofthis disclosure.

FIG. 18 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 19 is a diagrammatic perspective view of a transducer holder ofthis disclosure.

FIG. 20 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 21 is a diagrammatic perspective view of an absorbent element ofthis disclosure.

FIG. 22 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 23 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 24 is a diagrammatic perspective view of an absorbent element ofthis disclosure.

FIG. 25 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 26 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 27 is a diagrammatic perspective view of a part of a housing ofthis disclosure.

FIG. 28 is a diagrammatic perspective view of a circuit board of thisdisclosure.

FIG. 29 is a diagrammatic perspective view of a circuit board of thisdisclosure.

FIG. 30 is a diagrammatic exploded perspective view of a mist generatordevice of this disclosure.

FIG. 31 is a diagrammatic exploded perspective view of a mist generatordevice of this disclosure.

FIG. 32 is a cross sectional view of a mist generator device of thisdisclosure.

FIG. 33 is a cross sectional view of a mist generator device of thisdisclosure.

FIG. 34 is a cross sectional view of a mist generator device of thisdisclosure.

FIG. 35 is a diagrammatic exploded perspective view of a driver deviceof this disclosure.

FIG. 36 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 37 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 38 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 39 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 40 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 41 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 42 is a diagrammatic perspective view of part of a driver device ofthis disclosure.

FIG. 43 is a schematic diagram of an integrated circuit arrangement ofthis disclosure.

FIG. 44 is a schematic diagram of an integrated circuit of thisdisclosure.

FIG. 45 is a schematic diagram of a pulse width modulation generator ofthis disclosure.

FIG. 46 is timing diagram of an example of this disclosure.

FIG. 47 is timing diagram of an example of this disclosure.

FIG. 48 is a table showing port functions of an example of thisdisclosure.

FIG. 49 is a schematic diagram of an integrated circuit of thisdisclosure.

FIG. 50 is a circuit diagram of an H-bridge of an example of thisdisclosure.

FIG. 51 is a circuit diagram of a current sense arrangement of anexample of this disclosure.

FIG. 52 is a circuit diagram of an H-bridge of an example of thisdisclosure.

FIG. 53 is a graph showing the voltages during the phases of operationof the H-bridge of FIG. 50 .

FIG. 54 is a graph showing the voltages during the phases of operationof the H-bridge of FIG. 50 .

FIG. 55 is a graph showing the voltage and current at a terminal of anultrasonic transducer while the ultrasonic transducer is being driven bythe H-bridge of FIG. 50 .

FIG. 56 is a schematic diagram showing connections between integratedcircuits of this disclosure.

FIG. 57 is a schematic diagram of an integrated circuit of thisdisclosure.

FIG. 58 is diagram illustrating the steps of an authentication method ofan example of this disclosure.

FIG. 59 is a diagrammatic perspective view of an end cap of a driverdevice of this disclosure.

FIG. 60 is a diagrammatic perspective view of the housing of a driverdevice of this disclosure.

FIG. 61 is a graph showing the result of an EMC test for a mist inhalerdevice of this disclosure.

DETAILED DESCRIPTION

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components, concentrations, applicationsand arrangements are described below to simplify the present disclosure.These are, of course, merely examples and are not intended to belimiting. For example, the attachment of a first feature and a secondfeature in the description that follows may include embodiments in whichthe first feature and the second feature are attached in direct contact,and may also include embodiments in which additional features may bepositioned between the first feature and the second feature, such thatthe first feature and the second feature may not be in direct contact.In addition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

The following disclosure describes representative examples. Each examplemay be considered to be an embodiment and any reference to an “example”may be changed to “embodiment” in the present disclosure.

Some parts of the present disclosure are directed to an electronicvaporising inhaler. The specific example described below involvesnicotine. However, other examples are envisioned, such as an inhaler fortherapeutics, medicine, and herbal supplements. Additionally, the devicecan be packaged to look like a medical device which does not resemble acigarette.

Ultrasonic mist inhalers are either disposable or reusable. The term“reusable” as used herein implies that the energy storage device isrechargeable or replaceable or that the liquid is able to be replenishedeither through refilling or through replacement of the liquid reservoirstructure. Alternatively, in some examples reusable electronic device isboth rechargeable and the liquid can be replenished.

Conventional electronic vaporising inhaler tend to rely on inducing hightemperatures of a metal component configured to heat a liquid in theinhaler, thus vaporising the liquid that can be breathed in. The liquidtypically contains nicotine and flavourings blended into a solution ofpropylene glycol (PG) and vegetable glycerin (VG), which is vaporisedvia a heating component at high temperatures. Problems with conventionalinhaler may include the possibility of burning metal and subsequentbreathing in of the metal along with the burnt liquid. In addition, somemay not prefer the burnt smell or taste caused by the heated liquid.

FIG. 1 to FIG. 4 illustrates an example of an ultrasonic inhalercomprising a sonication chamber. FIG. 1 depicts a disposable ultrasonicmist inhaler 100. As can be seen in FIG. 1 , the ultrasonic mist inhaler100 has a cylindrical body with a relatively long length as compared tothe diameter. In the disposable example, the first portion and secondportion are regions of a single, but-separable device. The designationof a first portion 101 and a second portion 102 is used to convenientlydifferentiate the components that are primarily contained in eachportion.

As can be seen in FIG. 1 , the ultrasonic mist inhaler comprises amouthpiece 1, a liquid reservoir structure 2 and a casing 3. The firstportion 101 comprises the casing 3 and the second portion 102 comprisesthe mouthpiece 1 and the reservoir structure 2.

The first portion 101 contains the power supply energy.

An electrical storage device 30 powers the ultrasonic mist inhaler 100.The electrical storage device 30 can be a battery, including but notlimited to a lithium-ion, alkaline, zinc-carbon, nickel-metal hydride,or nickel-cadmium battery; a super capacitor; or a combination thereof.In the disposable example, the electrical storage device 30 is notrechargeable, but, in the reusable example, the electrical storagedevice 30 would be selected for its ability to recharge. In thedisposable example, the electrical storage device 30 is primarilyselected to deliver a constant voltage over the life of the inhaler 100.Otherwise, the performance of the inhaler would degrade over time.Preferred electrical storage devices that are able to provide aconsistent voltage output over the life of the device includelithium-ion and lithium polymer batteries.

The electrical storage device 30 has a first end 30 a that generallycorresponds to a positive terminal and a second end 30 b that generallycorresponds to a negative terminal. The negative terminal is extendingto the first end 30 a.

Because the electrical storage device 30 is located in the first portion101 and the liquid reservoir structure 2 is located in the secondportion 102, the joint needs to provide electrical communication betweenthose components. In the present invention, electrical communication isestablished using at least an electrode or probe that is compressedtogether when the first portion 101 is tightened into the second portion102.

In order for this example to be reusable, the electrical storage device30 is rechargeable. The casing 3 contains a charging port 32.

The integrated circuit 4 has a proximal end 4 a and a distal end 4 b.The positive terminal at the first end 30 a of the electrical storagedevice 30 is in electrical communication with a positive lead of theflexible integrated circuit 4. The negative terminal at the second end30 b of the electrical storage device 30 is in electrical communicationwith a negative lead of the integrated circuit 4. The distal end 4 b ofthe integrated circuit 4 comprises a microprocessor. The microprocessoris configured to process data from a sensor, to control a light, todirect current flow to means of ultrasonic vibrations 5 in the secondportion 102, and to terminate current flow after a pre-programmed amountof time.

The sensor detects when the ultrasonic mist inhaler 100 is in use (whenthe user draws on the inhaler) and activates the microprocessor. Thesensor can be selected to detect changes in pressure, air flow, orvibration. In one example, the sensor is a pressure sensor. In thedigital device, the sensor takes continuous readings which in turnrequires the digital sensor to continuously draw current, but the amountis small and overall battery life would be negligibly affected.

In some examples, the integrated circuit 4 comprises a H bridge, whichmay be formed by 4 MOSFETs to convert a direct current into an alternatecurrent at high frequency.

Referring to FIG. 2 and FIG. 3 , illustrations of a liquid reservoirstructure 2 according to an example are shown. The liquid reservoirstructure 2 comprises a liquid chamber 21 adapted to receive liquid tobe atomised and a sonication chamber 22 in fluid communication with theliquid chamber 21.

In the example shown, the liquid reservoir structure 2 comprises aninhalation channel 20 providing an air passage from the sonicationchamber 22 toward the surroundings.

As an example of sensor position, the sensor may be located in thesonication chamber 22.

The inhalation channel 20 has a frustoconical element 20 a and an innercontainer 20 b.

As depicted in FIGS. 4A and 4B, further the inhalation channel 20 has anairflow member 27 for providing air flow from the surroundings to thesonication chamber 22.

The airflow member 27 has an airflow bridge 27 a and an airflow duct 27b made in one piece, the airflow bridge 27 a having two airway openings27 a′ forming a portion of the inhalation channel 20 and the airflowduct 27 b extending in the sonication chamber 22 from the airflow bridge27 a for providing the air flow from the surroundings to the sonicationchamber.

The airflow bridge 27 a cooperates with the frustoconical element 20 aat the second diameter 20 a 2.

The airflow bridge 27 a has two opposite peripheral openings 27 a″providing air flow to the airflow duct 27 b.

The cooperation with the airflow bridge 27 a and the frustoconicalelement 20 a is arranged so that the two opposite peripheral openings 27a″ cooperate with complementary openings 20 a″ in the frustoconicalelement 20 a.

The mouthpiece 1 and the frustoconical element 20 a are radially spacedand an airflow chamber 28 is arranged between them.

As depicted in FIGS. 1 and 2 , the mouthpiece 1 has two oppositeperipheral openings 1″.

The peripheral openings 27 a″, 20 a″, 1″ of the airflow bridge 27 a, thefrustoconical element 20 a and the mouthpiece 1 directly supply maximumair flow to the sonication chamber 22.

The frustoconical element 20 a includes an internal passage, aligned inthe similar direction as the inhalation channel 20, having a firstdiameter 20 a 1 less than that of a second diameter 20 a 2, such thatthe internal passage reduces in diameter over the frustoconical element20 a.

The frustoconical element 20 a is positioned in alignment with the meansof ultrasonic vibrations 5 and a capillary element 7, wherein the firstdiameter 20 a 1 is linked to an inner duct 11 of the mouthpiece 1 andthe second diameter 20 a 2 is linked to the inner container 20 b.

The inner container 20 b has an inner wall delimiting the sonicationchamber 22 and the liquid chamber 21.

The liquid reservoir structure 2 has an outer container 20 c delimitingthe outer wall of the liquid chamber 21.

The inner container 20 b and the outer container 20 c are respectivelythe inner wall and the outer wall of the liquid chamber 21.

The liquid reservoir structure 2 is arranged between the mouthpiece 1and the casing 3 and is detachable from the mouthpiece 1 and the casing3.

The liquid reservoir structure 2 and the mouthpiece 1 or the casing 3may include complimentary arrangements for engaging with one another;further such complimentary arrangements may include one of thefollowing: a bayonet type arrangement; a threaded engaged typearrangement; a magnetic arrangement; or a friction fit arrangement;wherein the liquid reservoir structure 2 includes a portion of thearrangement and the mouthpiece 1 or the casing 3 includes thecomplimentary portion of the arrangement.

In the reusable example, the components are substantially the same. Thedifferences in the reusable example vis-a-vis the disposable example arethe accommodations made to replace the liquid reservoir structure 2.

As shown in FIG. 3 , the liquid chamber 21 has a top wall 23 and abottom wall 25 closing the inner container 20 b and the outer container20 c of the liquid chamber 21.

The capillary element 7 is arranged between a first section 20 b 1 and asecond section 20 b 2 of the inner container 20 b.

The capillary element 7 has a flat shape extending from the sonicationchamber to the liquid chamber.

As depicted in FIG. 2 or 3 , the capillary element 7 comprises a centralportion 7 a in U-shape and a peripheral portion 7 b in L-shape.

The L-shape portion 7 b extends into the liquid chamber 21 on the innercontainer 20 b and along the bottom wall 25.

The U-shape portion 7 a is contained into the sonication chamber 21. TheU-shape portion 7 a on the inner container 20 b and along the bottomwall 25.

In the ultrasonic mist inhaler, the U-shape portion 7 a has an innerportion 7 a 1 and an outer portion 7 a 2, the inner portion 7 a 1 beingin surface contact with an atomisation surface 50 of the means ofultrasonic vibrations 5 and the outer portion 7 a 2 being not in surfacecontact with the means of ultrasonic vibrations 5.

The bottom wall 25 of the liquid chamber 21 is a bottom plate 25 closingthe liquid chamber 21 and the sonication chamber 22. The bottom plate 25is sealed, thus preventing leakage of liquid from the sonication chamber22 to the casing 3.

The bottom plate 25 has an upper surface 25 a having a recess 25 b onwhich is inserted an elastic member 8. The means of ultrasonicvibrations 5 are supported by the elastic member 8. The elastic member 8is formed from an annular plate-shaped rubber having an inner hole 8′wherein a groove is designed for maintaining the means of ultrasonicvibrations 5.

The top wall 23 of the liquid chamber 21 is a cap 23 closing the liquidchamber 23.

The top wall 23 has a top surface 23 representing the maximum level ofthe liquid that the liquid chamber 21 may contain and the bottom surface25 representing the minimum level of the liquid in the liquid chamber21.

The top wall 23 is sealed, thus preventing leakage of liquid from theliquid chamber 21 to the mouthpiece 1.

The top wall 23 and the bottom wall 25 are fixed to the liquid reservoirstructure 2 by means of fixation such as screws, glue or friction.

As depicted in FIG. 3 , the elastic member is in line contact with themeans of ultrasonic vibrations 5 and prevents contact between the meansof ultrasonic vibrations 5 and the inhaler walls, suppression ofvibrations of the liquid reservoir structure are more effectivelyprevented. Thus, fine particles of the liquid atomised by the atomisingmember can be sprayed farther.

As depicted in FIG. 3 , the inner container 20 b has openings 20 b′between the first section 20 b 1 and the second section 20 b 2 fromwhich the capillary element 7 is extending from the sonication chamber21. The capillary element 7 absorbs liquid from the liquid chamber 21through the apertures 20 b′. The capillary element 7 is a wick. Thecapillary element 7 transports liquid to the sonication chamber 22 viacapillary action. In some examples, the capillary element 7 is made ofbamboo fibres. In some examples, the capillary element 7 may be of athickness between 0.27 mm and 0.32 mm and have a density between 38 g/m²and 48 g/m².

As can be seen in FIG. 3 , the means of ultrasonic vibrations 5 aredisposed directly below the capillary element 7.

The means of ultrasonic vibrations 5 may be a transducer. For example,the means of ultrasonic vibrations 5 may be a piezoelectric transducer,which may be designed in a circular plate-shape. The material of thepiezoelectric transducer may be ceramic.

A variety of transducer materials can also be used for the means ofultrasonic vibrations 5.

The end of the airflow duct 27 b 1 faces the means of ultrasonicvibrations 5. The means of ultrasonic vibrations 5 are in electricalcommunication with electrical contactors 101 a, 101 b. It is noted that,the distal end 4 b of the integrated circuit 4 has an inner electrodeand an outer electrode. The inner electrode contacts the firstelectrical contact 101 a which is a spring contact probe, and the outerelectrode contacts the second electrical contact 101 b which is a sidepin. Via the integrated circuit 4, the first electrical contact 101 a isin electrical communication with the positive terminal of the electricalstorage device 30 by way of the microprocessor, while the secondelectrical contact 101 b is in electrical communication with thenegative terminal of the electrical storage device 30.

The electrical contacts 101 a, 101 b crossed the bottom plate 25. Thebottom plate 25 is designed to be received inside the perimeter wall 26of the liquid reservoir structure 2. The bottom plate 25 rests oncomplementary ridges, thereby creating the liquid chamber 21 andsonication chamber 22.

The inner container 20 b comprises a circular inner slot 20 d on which amechanical spring is applied.

By pushing the central portion 7 a 1 onto the means of ultrasonicvibrations 5, the mechanical spring 9 ensures a contact surface betweenthem.

The liquid reservoir structure 2 and the bottom plate 25 can be madeusing a variety of thermoplastic materials.

When the user draws on the ultrasonic mist inhaler 100, an air flow isdrawn from the peripheral openings 1″ and penetrates the airflow chamber28, passes the peripheral openings 27 a″ of the airflow bridge 27 a andthe frustoconical element 20 a and flows down into the sonicationchamber 22 via the airflow duct 27 b directly onto the capillary element7. At the same time, the liquid is drawn from the reservoir chamber 21by capillarity, through the plurality of apertures 20 b′, and into thecapillary element 7. The capillary element 7 brings the liquid intocontact with the means of ultrasonic vibrations 5 of the inhaler 100.The user's draw also causes the pressure sensor to activate theintegrated circuit 4, which directs current to the means of ultrasonicvibrations 5. Thus, when the user draws on the mouthpiece 1 of theinhaler 100, two actions happen at the same time. Firstly, the sensoractivates the integrated circuit 4, which triggers the means ofultrasonic vibrations 5 to begin vibrating. Secondly, the draw reducesthe pressure outside the reservoir chamber 21 such that flow of theliquid through the apertures 20 b′ begins, which saturates the capillaryelement 7. The capillary element 7 transports the liquid to the means ofultrasonic vibrations 5, which causes bubbles to form in a capillarychannel by the means of ultrasonic vibrations 5 and mist the liquid.Then, the mist liquid is drawn by the user.

In some examples, the integrated circuit 4 comprises a frequencycontroller which is configured to control the frequency at which themeans of ultrasonic vibrations 5 operates. The frequency controllercomprises a processor and a memory, the memory storing executableinstructions which, when executed by the processor, cause the processorto perform at least one function of the frequency controller.

As described above, in some examples the ultrasonic mist inhaler 100drives the means of ultrasonic vibrations 5 with a signal having afrequency of 2.8 MHz to 3.2 MHz in order to vaporise a liquid having aliquid viscosity of 1.05 Pa·s to 1.412 Pa·s in order to produce a bubblevolume of about 0.25 to 0.5 microns. However, for liquids with adifferent viscosity or for other applications it the means of ultrasonicvibrations 5 may be driven at a different frequency.

For each different application for a mist generation system, there is anoptimum frequency or frequency range for driving the means of ultrasonicvibrations 5 in order to optimize the generation of mist. In exampleswhere the means of ultrasonic vibrations 5 is a piezoelectrictransducer, the optimum frequency or frequency range will depend on atleast the following four parameters:

1. Transducer Manufacturing Processes

In some examples, the means of ultrasonic vibrations 5 comprises apiezoelectric ceramic. The piezoelectric ceramic is manufactured bymixing compounds to make a ceramic dough and this mixing process may notbe consistent throughout production. This inconsistency can give rise toa range of different resonant frequencies of the cured piezoelectricceramic.

If the resonant frequency of the piezoelectric ceramic does notcorrespond to the required frequency of operation of the device then nomist is produced during the operation of the device. In the case of atherapeutic mist inhaler, even a slight offset in the resonant frequencyof the piezoelectric ceramic is enough to impact the production of mist,meaning that the device will not deliver adequate therapeutic levels tothe user.

2. Load on Transducer

During operation, any changes in the load on the piezoelectrictransducer will inhibit the overall displacement of the oscillation ofthe piezoelectric transducer. To achieve optimal displacement of theoscillation of the piezoelectric transducer, the drive frequency must beadjusted to enable the circuit to provide adequate power for maximumdisplacement.

The types of loads that can affect the oscillator's efficiency caninclude the amount of liquid on the transducer (dampness of the wickingmaterial), and the spring force applied to the wicking material to keeppermanent contact with the transducer. It may also include the means ofelectrical connection.

3. Temperature

Ultrasonic oscillations of the piezoelectric transducer are partiallydamped by its assembly in a device. This may include the transducerbeing placed in a silicone/rubber ring, and the spring exerting pressureonto the wicking material that is above the transducer. This dampeningof the oscillations causes rise in local temperatures on and around thetransducer.

An increase in temperature affects the oscillation due to changes in themolecular behaviour of the transducer. An increase in the temperaturemeans more energy to the molecules of the ceramic, which temporarilyaffects its crystalline structure. Although the effect is reversed asthe temperature reduces, a modulation in supplied frequency is requiredto maintain optimal oscillation. This modulation of frequency cannot beachieved with a conventional fixed frequency device.

An increase in temperature also reduces the viscosity of the solution(e-liquid) which is being vaporized, which may require an alteration tothe drive frequency to induce cavitation and maintain continuous mistproduction. In the case of a conventional fixed frequency device, areduction in the viscosity of the liquid without any change in the drivefrequency will reduce or completely stop mist production, rendering thedevice inoperable.

4. Distance to Power Source

The oscillation frequency of the electronic circuit can change dependingon the wire-lengths between the transducer and the oscillator-driver.The frequency of the electronic circuit is inversely proportional to thedistance between the transducer and the remaining circuit.

Although the distance parameter is primarily fixed in a device, it canvary during the manufacturing process of the device, reducing theoverall efficiency of the device. Therefore, it is desirable to modifythe drive frequency of the device to compensate for the variations andoptimise the efficiency of the device.

A piezoelectric transducer can be modelled as an RLC circuit in anelectronic circuit, as shown in FIG. 5 . The four parameters describedabove may be modelled as alterations to the overall inductance,capacitance, and/or resistance of the RLC circuit, changing theresonance frequency range supplied to the transducer. As the frequencyof the circuit increases to around the resonance point of thetransducer, the log Impedance of the overall circuit dips to a minimumand then rises to a maximum before settling to a median range.

FIG. 6 shows a generic graph explaining the change in overall impedancewith increase in frequency in an RLC circuit. FIG. 7 shows how apiezoelectric transducer acts as a capacitor in a first capacitiveregion at frequencies below a first predetermined frequency f_(s) and ina second capacitive region at frequencies above a second predeterminedfrequency f_(p). The piezoelectric transducer acts as an inductor in aninductive region at frequencies between the first and secondpredetermined frequencies f_(s), f_(p). In order to maintain optimaloscillation of the transducer and hence maximum efficiency, the currentflowing through the transducer must be maintained at a frequency withinthe inductive region.

The frequency controller of the device of some examples is configured tomaintain the frequency of oscillation of the piezoelectric transducer(the means of ultrasonic vibrations 5) within the inductive region, inorder to maximise the efficiency of the device.

The frequency controller is configured to perform a sweep operation inwhich the frequency controller drives the transducer at frequencieswhich track progressively across a predetermined sweep frequency range.As the frequency controller performs the sweep, the frequency controllermonitors an Analog-to-Digital Conversion (ADC) value of anAnalog-to-Digital converter which is coupled to the transducer. In someexamples the ADC value is a parameter of the ADC which is proportionalto the voltage across the transducer. In other examples, the ADC valueis a parameter of the ADC which is proportional to the current flowingthrough the transducer.

As will be described in more detail below, the frequency controller ofsome examples determines the active power being used by the ultrasonictransducer by monitoring the current flowing through the transducer.

During the sweep operation, the frequency controller locates theinductive region of the frequency for the transducer. Once the frequencycontroller has identified the inductive region, the frequency controllerrecords the ADC value and locks the drive frequency of the transducer ata frequency within the inductive region (i.e. between the first andsecond predetermined frequencies f_(s), f_(p)) in order to optimise theultrasonic cavitation by the transducer. When the drive frequency islocked within the inductive region, the electro-mechanical couplingfactor of the transducer is maximised, thereby maximising the efficiencyof the device.

In some examples, the frequency controller is configured to perform thesweep operation to locate the inductive region each time the oscillationis started or re-started. In the examples, the frequency controller isconfigured to lock the drive frequency at a new frequency within theinductive region each time the oscillation is started and therebycompensate for any changes in the parameters that affect the efficiencyof operation of the device.

In some examples, the frequency controller ensures optimal mistproduction and maximises efficiency of medication delivery to the user.In some examples, the frequency controller optimises the device andimproves the efficiency and maximises therapeutic delivery to the user.

In other examples, the frequency controller optimises the device andimproves the efficiency of any other device which uses ultrasound. Insome examples, the frequency controller is configured for use withultrasound technology for therapeutic applications in order to extendthe enhancement of drug release from an ultrasound-responsive drugdelivery system. Having precise, optimal frequency during operation,ensures that the microbubbles, nanobubbles, nanodroplets, liposome,emulsions, micelles or any other delivery systems are highly effective.

In some examples, in order to ensure optimal mist generation and optimaldelivery of compounds as described above, the frequency controller isconfigured to operate in a recursive mode. When the frequency controlleroperates in the recursive mode, the frequency controller runs the sweepof frequencies periodically during the operation of the device andmonitors the ADC value to determine if the ADC value is above apredetermined threshold which is indicative of optimal oscillation ofthe transducer.

In some examples, the frequency controller runs the sweep operationwhile the device is in the process of aerosolising liquid in case thefrequency controller is able to identify a possible better frequency forthe transducer. If the frequency controller identifies a betterfrequency, the frequency controller locks the drive frequency at thenewly identified better frequency in order to maintain optimal operationof the device.

In some examples, the frequency controller runs the sweep of frequenciesfor a predetermined duration periodically during the operation of thedevice. In the case of the device of the examples described above, thepredetermined duration of the sweep and the time period between sweepsare selected to optimise the functionality of the device. Whenimplemented in an ultrasonic mist inhaler device, this will ensure anoptimum delivery to a user throughout the user's inhalation.

FIG. 8 shows a flow diagram of the operation of the frequency controllerof some examples.

The following disclosure discloses further examples of mist inhalerdevices which comprise many of the same elements as the examplesdescribed above. Elements of the examples described above may beinterchanged with any of the elements of the examples described in theremaining part of this disclosure.

To ensure adequate aerosol production, in this example the mist inhalerdevice comprises an ultrasonic/piezoelectric transducer of exactly orsubstantially 16 mm diameter. This transducer is manufactured tospecific capacitance and impedance values to control the frequency andpower required for desired aerosol volume production.

A horizontally placed disc-shaped 16 mm diameter ultrasonic transducerwould result in a large device that may not be ergonomic as handheld. Tomitigate this concern, the ultrasonic transducer of this example is heldvertically in the sonication chamber (the planar surface of theultrasonic transducer is generally parallel with the flow of aerosolmist to the mouthpiece and/or generally parallel to the longitudinallength of the mist inhaler device). Put another way, the ultrasonictransducer is generally perpendicular to a base of the mist inhalerdevice.

Referring now to FIGS. 9 and 10 of the accompanying drawings, a mistinhaler device 200 of some examples comprises a mist generator device201 and a driver device 202. The driver device 202 is, in this example,provided with a recess 203 which receives and retains part of the mistgenerator device 201. The mist generator 201 can therefore be coupledwith the driver device 202 to form a compact and portable mist inhalerdevice 200, as shown in FIG. 9 .

Referring now to FIGS. 11 to 13 of the accompanying drawings, the mistgenerator device 201 comprises a mist generator housing 204 which iselongate and optionally formed from two housing portions 205, 206 whichare attached to one another. The mist generator housing 204 comprises anair inlet port 207 and a mist outlet port 208.

In this example, the mist generator housing 204 is of injection mouldedplastic, specifically polypropylene that is typically used for medicalapplications. In this example, the mist generator housing 204 is of aheterophasic copolymer. More particularly a BF970MO heterophasiccopolymer, which has an optimum combination of very high stiffness andhigh impact strength. The mist generator housing parts moulded with thismaterial exhibit good anti-static performance.

A heterophasic copolymer such as polypropylene is particularly suitablefor the mist generator housing 204 since this material does not causecondensation of the aerosol as it flows from the sonication chamber 219through the mouthpiece to the user. This plastic material can also bedirectly recycled easily using industrial shredding and cleaningprocesses.

In FIGS. 9, 10 and 12 , the mist outlet port 208 is closed by a closureelement 209. However, it is to be appreciated that when the mist inhalerdevice 200 is in use, the closure element 209 is removed from the mistoutlet port 208, as shown in FIG. 11 .

Referring now to FIGS. 14 and 15 , the mist generator device 200comprises a transducer holder 210 which is held within the mistgenerator housing 204. The transducer holder 210 comprises a bodyportion 211 which, in this example, is cylindrical or generallycylindrical in shape with circular upper and lower openings 212, 213.The transducer holder 210 is provided with an internal recess 214 forreceiving an edge of an ultrasonic transducer 215, as shown in FIG. 15 .

The transducer holder 210 incorporates a cutaway section 216 throughwhich an electrode 217 extends from the ultrasonic transducer 215 sothat the electrode 217 may be connected electrically to an AC driver ofthe drive device, as described in more detail below.

Referring again to FIG. 13 , the mist generator device 201 comprises aliquid chamber 218 which is provided within the mist generator housing204. The liquid chamber 218 is for containing a liquid, such as atherapeutic liquid, to be atomised. In some examples, a liquid iscontained in the liquid chamber 218. In other examples, the liquidchamber 218 is empty initially and the liquid chamber is filled with aliquid subsequently.

The liquid preferably includes at least one therapeutic suitable for theaerosol delivery to the lungs through inhalation by a patient forproviding a desired treatment to the patient. Some examples oftherapeutics include, but are not limited to, aerosol delivery ofpharmacological agents to the lungs to promote a systemic or directclinical effect while producing a minimal adverse-effect. A therapeuticmay also include for example, but not limited to, natural drugs,cannabinoid derivatives such as CBD for pain relief and othertreatments; botanicals; opioids; RNA; DNA; chemotherapies; subcellularcomponents including for example ribosomes, endoplasmic reticulum,cytoskeleton, and mitochondria; supplements for performance enhancement;albuterol/salbutamol for asthma patients; agents such as beta-lactams,polymyxins, and aminoglycosides bactericidal antibiotics; amphotericinB; morphine; fentanyl; prostacyclin, amiloride, and interferon-g; andcyclosporine as rescue therapy rejection in lung-transplantationpatients and a treatment for asthma.

The following description refers to nicotine, but in other examples ofthis disclosure the nicotine is replaced with a therapeutic, such as,but not limited to one or more of the therapeutics described herein.

A liquid (also referred to herein as an e-liquid) composition suitablefor use in an ultrasonic device that is powered at a frequency of 3.0MHz (±0.2 MHz) by a 3.7V lithium polymer (LiPo) battery consisting of anicotine salt consisting of nicotine levulinate wherein:

The relative amount of vegetable glycerin in the composition is: from 55to 80% (w/w), or from 60 to 80% (w/w), or from 65 to 75% (w/w), or 70%(w/w); and/or,

The relative amount of propylene glycol in the composition is: from 5 to30% (w/w), or from 10 to 30% (w/w), or from 15 to 25% (w/w), or 20%(w/w); and/or,

The relative amount of water in the composition is: from 5 to 15% (w/w),or from 7 to 12% (w/w), or 10% (w/w); and/or,

The amount of nicotine and/or nicotine salt in the composition is: from0.1 to 80 mg/ml, or from 0.1 to 50 mg/ml, or from 1 to 25 mg/ml, or from10 to 20 mg/ml, or 17 mg/ml.

In some examples, the mist generator device 201 contains an e-liquidhaving a kinematic viscosity between 1.05 Pa·s and 1.412 Pa·s.

In some examples, the liquid chamber 218 contains a liquid comprising anicotine levulinate salt at a 1:1 molar ratio.

In some examples, the liquid chamber 218 contains a liquid having akinematic viscosity between 1.05 Pa·s and 1.412 Pa·s and a liquiddensity between 1.1 g/ml and 1.3 g/ml.

By using an e-liquid with the correct parameters of viscosity, densityand having a desired target bubble volume of liquid spray into the air,it has been found that the frequency range of 2.8 MHz to 3.2 MHz forliquid viscosity range of 1.05 Pass and 1.412 Pass and density ofapproximately 1.1-1.3 g/mL (get density ranges from Hertz) produce adroplet volume where 90% of droplets are below 1 micron and 50% of thoseare less than 0.5 microns.

The mist generator device 201 comprises a sonication chamber 219 whichis provided within the mist generator housing 204.

Returning to FIGS. 14 and 15 , the transducer holder 210 comprises adivider portion 220 which provides a barrier between the liquid chamber218 and the sonication chamber 219. The barrier provided by the dividerportion 220 minimises the risk of the sonication chamber 219 being isflooded with liquid from the liquid chamber 218 or for a capillaryelement over the ultrasonic transducer 215 becoming oversaturated,either of which would overload and reduce the efficiency of theultrasonic transducer 215. Moreover, flooding the sonication chamber 219or over saturating the capillary element could also cause an unpleasantexperience with the liquid being sucked in by the user duringinhalation. To mitigate this risk, the divider portion 220 of thetransducer holder 210 sits as a wall between the sonication chamber 219and the liquid chamber 218.

The divider portion 220 comprises a capillary aperture 221 which is theonly means by which liquid can flow from the liquid chamber 218 to thesonication chamber 219, via a capillary element. In this example, thecapillary aperture 221 is an elongate slot having a width of 0.2 mm to0.4 mm. The dimensions of the capillary aperture 221 are such that theedges of the capillary aperture 221 provide a biasing force which actson a capillary element extending through the capillary aperture 221 foradded control of liquid flow to the sonication chamber 219.

In this example, the transducer holder 210 is of liquid silicone rubber(LSR). In this example, the liquid silicone rubber has a Shore A 60hardness. This LSR material ensures that the ultrasonic transducer 215vibrates without the transducer holder 210 dampening the vibrations. Inthis example, the vibratory displacement of the ultrasonic transducer215 is 2-5 nanometres and any dampening effect may reduce the efficiencyof the ultrasonic transducer 215. Hence, this LSR material and hardnessis selected for optimal performance with minimal compromise.

Referring now to FIGS. 16 and 17 , the mist generator device 201comprises a capillary or capillary element 222 for transferring a liquid(containing a drug or other substance) from the liquid chamber 218 tothe sonication chamber 219. The capillary element 222 is planar orgenerally planar with a first portion 223 and a second portion 224. Inthis example, the first portion 223 has a rectangular or generallyrectangular shape and the second portion 224 has a partly circularshape.

In this example, the capillary element 222 comprises a third portion 225and a fourth portion 226 which are respectively identical in shape tothe first and second portions 223, 224. The capillary element 222 ofthis example is folded about a fold line 227 such that the first andsecond portions 223, 224 and the third and fourth portions 225, 226 aresuperimposed on one another, as shown in FIG. 17 .

In this example, the capillary element has a thickness of approximately0.28 mm. When the capillary element 222 is folded to have two layers, asshown in FIG. 17 , the overall thickness of the capillary element isapproximately 0.56 mm. This double layer also ensures that there isalways sufficient liquid on the ultrasonic transducer 215 for optimalaerosol production.

In this example, when the capillary element 222 is folded, the lower endof the first and third parts 223, 225 defines an enlarged lower end 228which increases the surface area of the capillary element 222 in theportion of the capillary element 222 which sits in liquid within theliquid chamber 218 to maximise the rate at which the capillary element222 absorbs liquid.

In this example, the capillary element 222 is 100% bamboo fibre. Inother examples, the capillary element is of at least 75% bamboo fibre.The benefits of using bamboo fibre as the capillary element are asdescribed above.

Referring now to FIGS. 18 and 19 , the capillary element 222 is retainedby the transducer holder 210 such that the transducer holder 210 retainsthe second portion 224 of the capillary element 222 superimposed on partof an atomisation surface of the ultrasonic transducer 215. In thisexample, the circular second portion 224 sits within the internal recess214 of the transducer holder 210.

The first portion 223 of the capillary element 222 extends through thecapillary aperture 221 in the transducer holder 210.

Referring now to FIGS. 20 to 22 , the second portion 206 of the mistgenerator housing 204 comprises a generally circular wall 229 whichreceives the transducer holder 210 and forms part of the wall of thesonication chamber 219.

Contact apertures 230 and 231 are provided in a side wall of the secondportion 206 for receiving electrical contacts 232 and 233 which formelectrical connections with the electrodes of the ultrasonic transducer215.

In this example, an absorbent tip or absorbent element 234 is providedadjacent the mist outlet port 208 to absorb liquid at the mist outletport 208. In this example, the absorbent element 234 is of bamboo fibre.

Referring now to FIGS. 23 to 25 , the first portion 205 of the mistgenerator housing 204 is of a similar shape to the second portion 206and comprises a further generally circular wall portion 235 which formsa further portion of the wall of the sonication chamber 219 and retainsthe transducer holder 210.

In this example, a further absorbent element 236 is provided adjacentthe mist outlet port 208 to absorb liquid at the mist outlet port 208.

In this example, the first portion 205 of the mist generator housing 204comprises a spring support arrangement 237 which supports the lower endof a retainer spring 238, as shown in FIG. 26 .

An upper end of the retainer spring 238 contacts the second portion 224of the capillary element 222 such that the retainer spring 238 providesa biasing force which biases the capillary element 222 against theatomisation surface of the ultrasonic transducer 215.

Referring to FIG. 27 , the transducer holder 210 is shown in positionand being retained by the second portion 206 of the mist generatorhousing 204, prior to the two portions 205, 206 of the mist generatorhousing 204 being attached to one another.

Referring to FIGS. 28 to 31 , in this example, the mist generator device201 comprises an identification arrangement 239. The identificationarrangement 239 comprises a printed circuit board 240 having electricalcontacts 241 provided on one side and an integrated circuit 242 andanother optional component 243 provided on the other side.

The integrated circuit 242 has a memory which stores a unique identifierfor the mist generator device 201. The electrical contacts 241 providean electronic interface for communication with the integrated circuit242.

The printed circuit board 240 is, in this example, mounted within arecess 244 on one side of the mist generator housing 204. The integratedcircuit 242 and optional other electronic components 243 sit within afurther recess 245 so that the printed circuit board 240 is generallyflush with the side of the mist generator housing 204.

In this example, the integrated circuit 242 is a one-time-programmable(OTP) device which is an anti-counterfeiting feature that allows onlygenuine mist generator devices from the manufacturer to be used with thedevice. This anti-counterfeiting feature is implemented in the mistgenerator device 201 as a specific custom integrated circuit (IC) thatis bonded (with the printed circuit board 240) to the mist generatordevice 201. The OTP as IC contains a truly unique information thatallows a complete traceability of the mist generator device 201 (and itscontent) over its lifetime as well as a precise monitoring of theconsumption by the user. The OTP IC allows the mist generator device 201to function to generate mist only when authorised.

An implementation of the OTP IC of an example of this disclosure isdescribed in detail below.

The OTP, as a feature, dictates the authorised status of a specific mistgenerator device 201. Indeed, in order to prevent emissions of carbonylsand keep the aerosol at safe standards, experiments have shown that themist generator device 201 is considered empty of liquid in the liquidchamber 218 after approximately 1,000 seconds of aerosolisation. In thatway a mist generator device 201 that is not genuine or empty will not beable to be activated after this predetermined duration of use.

The OTP, as a feature, may be part of a complete chain with theconjunction of the digital sale point, the mobile companion applicationand the mist generator device 201. Only a genuine mist generator device201 manufactured by a trusted party and sold on the digital sale pointcan be used in the device. A mobile companion digital app, being a linkbetween the user account on a manufacturer's digital platform and themist generator device 201, ensures safe usage of a known safe contentfor a safe amount of puff duration.

The OTP, as a feature, also enables high access control and monitoringrequired as per medical drug administration in the case of business tobusiness (B2B) use with trusted health establishments. The OTP IC isread by the driver device 202 which can recognise the mist generatordevice 201 inserted and the prescription associated with it. The driverdevice 202 cannot be used with this mist generator device 201 more thannor outside of the time frame specified by the prescription. In additiona reminder on the mobile companion app can be provided to minimise auser missing a dose.

In some examples, the OTP IC is disposable in the same way as the mistgenerator device 201. Whenever the mist generator device 201 isconsidered empty, it will not be activated if inserted into a driverdevice 202. Similarly, a counterfeit generator device 201 would not befunctional in the driver device 202.

FIGS. 32 to 34 illustrate how air flows through the mist generatordevice 201 during operation.

The sonication of the liquid therapeutic (medical solutions, medicalsuspensions, protein solutions, supplements, etc.) transforms it intomist (aerosolisation). However, this mist would settle over theultrasonic transducer 215 unless enough ambient air is available toreplace the rising aerosol. In the sonication chamber 219, there is arequirement for a continuous supply of air as mist (aerosol) isgenerated and pulled out through the mouthpiece to the user. To cater tothis requirement, an airflow channel is provided. In this example theairflow channel has an average cross-sectional area of 11.5 mm², whichis calculated and designed into the sonication chamber 219 based on thenegative air pressure from an average user. This also controls themist-to-air ratio of the inhaled aerosol, controlling the amount of drugdelivered to the user.

Based on design requirements, the air flow channel is routed such thatit initiates from the bottom of the sonication chamber 219. The openingat the bottom of the aerosol chamber aligns with and is tightly adjacentto the opening to an airflow bridge in the device. The air flow channelruns vertically upwards along the reservoir and continues until thecentre of the sonication chamber (concentric with the ultrasonictransducer 215). Here, it turns 90° inwards. The flow path thencontinues on until approximately 1.5 mm from the ultrasonic transducer215. This routing ensures maximised ambient air supplied directly in thedirection of the atomisation surface of the ultrasonic transducer 215.The airflows through the channel, towards the transducer, collects thegenerated mist as it travels out through the mouthpiece and to the user.

The driver device 202 will now be described with reference to FIGS. 35and 36 initially. Air flows into the mist generator device 201 via theair inlet port 207 which, as described below, is in fluid communicationwith an airflow bridge within the driver device 202. The air flows alonga flow path which changes the direction of the air flow by approximately90° to direct the flow of air towards the ultrasonic transducer 215.

In some examples, the airflow arrangement is configured to change thedirection of a flow of air along the air flow path such that the flow ofair is substantially perpendicular to the atomisation surface of theultrasonic transducer as the flow of air passes into the sonicationchamber.

The driver device 202 comprises a driver device housing 246 which is atleast partly of metal. In some examples, the driver device housing 246is entirely of aluminium (AL6063 T6) which protects the internalcomponents from the environment (dust, water splashes, etc.) and alsoprotects from damage from shocks (accidental drops, etc.).

In some examples, the driver device housing 246 is provided with ventson its sides that allow ambient air to enter the device for twopurposes; one to have ventilation around the electronic components andkeep them within operating temperatures, and these vents also act as airinlets with air entering through these vents into the device, and thenthrough the airflow bridge into the mist generator device 201.

The driver device housing 246 is elongate with an internal chamber 247which houses the components of the driver device 202. One end of thedriver device housing 246 is closed by an end cap 248. The other end ofthe driver device housing 247 has an opening 249 which provides anopening for the recess 203 of the driver device 202.

The driver device 202 comprises a battery 250 which is connected to aprinted circuit board 251. In some examples, the battery 250 is a 3.7VDC Li—Po battery with 1140 mAh capacity and 10 C discharge rate. Thehigh discharge rate is required for voltage amplification of up to 15Vthat is required by the ultrasonic transducer 215 for desirableoperation. The shape and size of the battery is designed, withinphysical constraints, as per the shape and size of the device and spaceallocated for the power source.

The printed circuit board 251 incorporates a processor and a memory andother electronic components for implementing the electrical functions ofthe driver device 202. Charging pins 258 are provided on one end of theprinted circuit board 251 and which extend through the end cap 248 toprovide charging connections to charge the battery 250.

The printed circuit board 251 is retained within the driver devicehousing 246 by a skeleton 252. The skeleton 252 has a channel 253 whichreceives the printed circuit board 251. The skeleton 252 incorporatesraised side portions 254, 255 which support the battery 250.

In some examples, the skeleton 252 is manufactured using industrialinjection moulding processes. The moulded plastic skeleton ensures allparts are fixed and not loosely fitting inside the case. It also forms acover over the front part of the PCB (Printed Circuit Board) whichreceived the mist generator device 201 when it is inserted into thedriver device 202.

The driver device 202 comprises an airflow sensor which acts as a switchfor activating and supplying power to the transducer for sonication andaerosol production. The airflow sensor is mounted onto the PCB in thedevice and requires a certain atmospheric pressure drop around it toactivate the driver device 202. For this, an airflow bridge 259 as shownin FIGS. 39 to 41 is designed with internal channels 260, 261 thatdirect air from the surrounding in through the bridge 259 into theaerosol chamber 262. The skeleton 252 comprises opposing channels 256,257 for receiving portions of the airflow bridge 259, as shown in FIG.42 .

The internal channels in the airflow bridge 259 have a micro-channel 263(0.5 mm diameter) that extends down towards a chamber 264 thatcompletely covers the airflow sensor. As the air flows in from the sideinlets and upwards to the aerosol chamber 262, it creates a negativepressure in the micro-channel 263 that triggers the airflow sensor toactivate the device.

The device is a compact, portable and highly advanced device that allowsprecise, safe and monitored aerosolisation. This is done byincorporating high-quality electronic components designed with IPC class3—medical grade—in mind.

The electronics of the driver device 202 are divided as such:

1. Sonication Section

In order to obtain the most efficient aerosolisation to date forinhalation in a portable device, with particle size below 1 um, thesonication section has to provide the contacts pads receiving theultrasonic transducer 215 (piezoelectrical ceramic disc (PZT)) with highadaptive frequency (approximately 3 MHz).

This section not only has to provide high frequency but also protect theultrasonic transducer 215 against failures while providing constantoptimised cavitation.

PZT mechanical deformation is linked to the AC Voltage amplitude that isapplied to it, and in order to guarantee optimal functioning anddelivery of the system at every sonication, the maximum deformation mustbe supplied to the PZT all the time.

However, in order to prevent the failure of the PZT, the active powertransferred to it must be precisely controlled.

This could only be achieved by designing a custom, not existing in themarket, Power Management Integrated Circuit (PMIC) chip which isprovided on the printed circuit board of the driver device 202. ThisPMIC allows modulation of the active power given to the PZT at everyinstant without compromising the mechanical amplitude of vibration ofthe PZT.

By Pulse Width Modulation (PWM) of the AC voltage applied to the PZT,the mechanical amplitude of the vibration remains the same.

The only ‘on the shelf’ option available would have been to modify theoutput AC voltage via the use of a Digital to Analog Converter (DAC).The energy transmitted to the PZT would be reduced but so would themechanical deformation which as a result completely degrades andprevents proper aerosolisation. Indeed, the RMS voltage applied would bethe same with effective Duty Cycle modulation as with Voltagemodulation, but the active power transferred to the PZT would degrade.Indeed, given the formula below:

Active Power displayed to the PZT being

${{Pa} = {\frac{2\sqrt{2}}{\pi}{Irms}*{Vrms}*\cos\varphi}},$

Where

φ is the shift in phase between current and voltage

I_(rms) is the root mean square Current

V_(rms) is the root mean square Voltage.

When considering the first harmonic, Irms is a function of the realvoltage amplitude applied to the transducer, as the pulse widthmodulation alters the duration of voltage supplied to the transducer,controlling Irms.

The specific design of the PMIC uses a state-of-the-art design, enablingultra-precise control of the frequency range and steps to apply to thePZT including a complete set of feedback loops and monitoring path forthe control section to use.

The rest of the aerosolisation section is composed of the DC/DC boostconverter and transformer that carry the necessary power from a 3.7Vbattery to the PZT contact pads.

Referring now to FIG. 43 of the accompanying drawings, the driver device202 comprises an ultrasonic transducer driver microchip which isreferred to herein as a power management integrated circuit or PMIC 300.The PMIC 300 is a microchip for driving a resonant circuit. The resonantcircuit is an LC tank, an antenna or, in this case, a piezoelectrictransducer (the ultrasonic transducer 215).

In this disclosure, the terms chip, microchip and integrated circuit areinterchangeable. The microchip or integrated circuit is a single unitwhich comprises a plurality of interconnected embedded components andsubsystems. The microchip is, for example, at least partly of asemiconductor, such as silicon, and is fabricated using semiconductormanufacturing techniques.

The driver device 202 also comprises a second microchip which isreferred to herein as a bridge integrated circuit or bridge IC 301 whichis electrically connected to the PMIC 300. The bridge IC 301 is amicrochip for driving a resonant circuit, such as an LC tank, an antennaor a piezoelectric transducer. The bridge IC 301 is a single unit whichcomprises a plurality of interconnected embedded components andsubsystems.

In this example, the PMIC 300 and the bridge IC 301 are mounted to thesame PCB of the driver device 202. In this example, the physicaldimensions of the PMIC 300 are 1-3 mm wide and 1-3 mm long and thephysical dimensions of the bridge IC 301 are 1-3 mm wide and 1-3 mmlong.

The mist generator device 201 comprises a programmable or one timeprogrammable integrated circuit or OTP IC 242. When the mist generatordevice 201 is coupled to the driver device 202, the OTP IC iselectrically connected to the PMIC 300 to receive power from the PMIC300 such that the PMIC 300 can manage the voltage supplied to the OTP IC242. The OTP IC 242 is also connected to a communication bus 302 in thedriver device 202. In this example, the communication bus 302 is an I2Cbus but in other examples the communication bus 302 is another type ofdigital serial communication bus.

The ultrasonic transducer 215 in the mist generator device 201 iselectrically connected to the bridge IC 301 so that the ultrasonictransducer 215 may be driven by an AC drive signal generated by thebridge IC 301 when the device 200 is in use.

The driver device 202 comprises a processor in the form of amicrocontroller 303 which is electrically coupled for communication withthe communication bus 302. In this example, the microcontroller 303 is aBluetooth™ low energy (BLE) microcontroller. The microcontroller 303receives power from a low dropout regulator (LDO) 304 which is driven bythe battery 250. The LDO 304 provides a stable regulated voltage to themicrocontroller 303 to enable the microcontroller 303 to operateconsistently even when there is a variation in the voltage of thebattery 250.

The driver device 202 comprises a voltage regulator in the form of aDC-DC boost converter 305 which is powered by the battery 250. The boostconverter 305 increases the voltage of the battery 250 to a programmablevoltage VBOOST. The programmable voltage VBOOST is set by the boostconverter 305 in response to a voltage control signal VCTL from the PMIC300. As will be described in more detail below, the boost converter 305outputs the voltage VBOOST to the bridge IC 301. In other examples, thevoltage regulator is a buck converter or another type of voltageregulator which outputs a selectable voltage.

The voltage control signal VCTL is generated by a digital to analogueconverter (DAC) which, in this example, is implemented within the PMIC300. The DAC is not visible in FIG. 43 since the DAC is integratedwithin the PMIC 300. The DAC and the technical benefits of integratingthe DAC within the PMIC 300 are described in detail below.

In this example, the PMIC 300 is connected to a power source connectorin the form of a universal serial bus (USB) connector 306 so that thePMIC 300 can receive a charging voltage VCHRG when the USB connector 306is coupled to a USB charger.

The driver device 202 comprises a first pressure sensor 307 which, inthis example, is a static pressure sensor. The driver device 202 alsocomprises a second pressure sensor 308 which, in this example, is adynamic pressure sensor. However, in other examples, the driver device202 comprises only one of the two pressure sensors 307, 308. Asdescribed above, the pressure sensors 307, 308 sense a change in thepressure in the aerosol chamber 262 to sense when a user is drawing onthe mist inhaler device 200.

In this example, the driver device 202 comprises a plurality of LEDs321-326 which are controlled by the PMIC 300.

The microcontroller 303 functions as a master device on thecommunication bus 302, with the PMIC 300 being a first slave device, theOTP IC 242 being a second slave device, the second pressure sensor 308being a third slave device and the first pressure sensor 307 being the afourth slave device. The communication bus 302 enables themicrocontroller 303 to control the following functions within the driverdevice 202:

-   -   1. All functions of the PMIC are highly configurable by the        microcontroller 303.    -   2. The current flowing through the ultrasonic transducer 215 is        sensed by a high bandwidth sense and rectifier circuit at a high        common mode voltage (high side of the bridge). The sensed        current is converted into a voltage proportional to the rms        current and provided as a buffered voltage at a current sense        output pin 309 of the bridge IC 301. This voltage is fed to and        sampled in the PMIC 300 and made available as a digital        representation via I2C requests. Sensing the current flowing        through the ultrasonic transducer 215 forms part of the resonant        frequency tracking functionality. As described herein, the        ability of the device to enable this functionality within the        bridge IC 301 provides significant technical benefits.    -   3. The DAC (not shown in FIG. 43 ) integrated within the PMIC        300 enables the DC-DC boost converter voltage VBOOST to be        programmed to be between 10V and 20V.

4. The microcontroller 303 enables the charger sub-system of the driverdevice 202 to manage the charging of the battery 250, which in thisexample is a single cell battery.

5. A Light Emitting Diode (LED) driver module (not shown) is powered bythe PMIC 300 to drive and dim digitally the LEDs 321-326 either inlinear mode or in gamma corrected mode.

-   -   6. The microcontroller 303 is able to read Pressure #1 and        Pressure #2 sensor values from the pressure sensors 307, 308.

Referring now to FIG. 44 of the accompanying drawings, the PMIC 300 is,in this example, a self-contained chip or integrated circuit whichcomprises integrated subsystems and a plurality of pins which provideelectrical inputs and outputs to the PMIC 300. The references to anintegrated circuit or chip in this disclosure are interchangeable andeither term encompasses a semiconductor device which may, for instance,be of silicon.

The PMIC 300 comprises an analogue core 310 which comprises analoguecomponents including a reference block (BG) 311, a LDO 312, a currentsensor 313, a temperature sensor 314 and an oscillator 315.

As described in more detail below, the oscillator 315 is coupled to adelay locked loop (DLL) which outputs pulse width modulation (PWM)phases A and B. The oscillator 315 and the DLL generate a two phasecentre aligned PWM output which drives an H bridge in the bridge IC 301.

The DLL comprises a plurality of delay lines connected end to end,wherein the total delay of the delay lines is equal to the period of themain clock signal clk_m. In this example, the DLL is implemented in adigital processor subsystem, referred to herein as a digital core 316,of the PMIC 300 which receives a clock signal from the oscillator 315and a regulated power supply voltage from the LDO 312. The DLL isimplemented in a large number (e.g. in the order of millions) of delaygates which are connected end to end in the digital core 316.

The implementation of the oscillator 315 and the DLL in the sameintegrated circuit of the PMIC 300 in order to generate a two phasecentre aligned PWM signal is unique since at present no signal generatorcomponent in the integrated circuit market comprises thisimplementation.

As described herein, PWM is part of the functionality which enables thedriver device 202 to track the resonant frequency of the ultrasonictransducer 215 accurately in order to maintain an efficient transferfrom electrical energy to kinetic energy in order to optimise thegeneration of mist.

In this example, the PMIC 300 comprises a charger circuit 317 whichcontrols the charging of the battery 250, for instance by power from aUSB power source.

The PMIC 300 comprises an integrated power switch VSYS which configuresthe PMIC 300 to power the analogue core 310 by power from the battery250 or by power from an external power source if the battery 250 isbeing charged.

The PMIC 300 comprises an embedded analogue to digital converter (ADC)subsystem 318. The implementation of the ADC 318 together with theoscillator 315 in the same integrated circuit is, in itself, uniquesince there is no other integrated circuit in the integrated circuitmarket which comprises an oscillator and an ADC implemented assub-blocks within the integrated circuit. In a conventional device, anADC is typically provided as a separate discrete component from anoscillator with the separate ADC and oscillator being mounted to thesame PCB. The problem with this conventional arrangement is that the twoseparate components of the ADC and the oscillator take up spaceunnecessarily on the PCB. A further problem is that the conventional ADCand oscillator are usually connected to one another by a serial datacommunication bus, such as an I2C bus, which has a limited communicationspeed of up to only 400 kHz. In contrast to conventional devices, thePMIC 300 comprises the ADC 318 and the oscillator 315 integrated withinthe same integrated circuit which eliminates any lag in communicationbetween the ADC 318 and the oscillator 315, meaning that the ADC 318 andthe oscillator 315 can communicate with one another at high speed, suchas at the speed of the oscillator 315 (e.g. 3 MHz to 5 MHz).

In the PMIC 300 of this example, the oscillator 315 is running at 5 MHzand generates a clock signal SYS CLOCK at 5 MHz. However, in otherexamples, the oscillator 315 generates a clock signal at a much higherfrequency of up to 105 MHz. The integrated circuits described herein areall configured to operate at the high frequency of the oscillator 315.

The ADC 318 comprises a plurality of feedback input terminals oranalogue inputs 319 which comprise a plurality of GPIO inputs(IF_GPIO1-3). At least one of the feedback input terminals or theanalogue inputs 319 receives a feedback signal from an H-bridge circuitin the bridge IC 301, the feedback signal being indicative of aparameter of the operation of the H-bridge circuit or an AC drive signalwhen the H-bridge circuit is driving a resonant circuit, such as theultrasonic transducer 215, with the AC drive signal. As described below,the GPIO inputs are used to receive a current sense signal from thebridge IC 301 which is indicative of the route mean square (rms) currentreported by the bridge IC 301. In this example, one of the GPIO inputsis a feedback input terminal which receives a feedback signal from theH-bridge in the bridge IC 301.

The ADC subsystem 318 samples analogue signals received at the pluralityof ADC input terminals 319 at a sampling frequency which is proportionalto the frequency of the main clock signal. The ADC subsystem 318 thengenerates ADC digital signals using the sampled analogue signals.

In this example, the ADC 318 which is incorporated in the PMIC 300samples not only the RMS current flowing through the H-bridge 334 andthe ultrasonic transducer 215 but also voltages available in the system(e.g. VBAT, VCHRG, VBOOST), the temperature of the PMIC 300, thetemperature of the battery 250 and the GPIO inputs (IF_GPIO1-3) whichallow for future extensions.

The digital core 316 receives the ADC generated digital signals from theADC subsystem and processes the ADC digital signals to generate thedriver control signal. The digital core 316 communicates the drivercontrol signal to the PWM signal generator subsystem (DLL 332) tocontrol the PWM signal generator subsystem.

Rectification circuits existing in the market today have a very limitedbandwidth (typically less than 1 MHz). Since the oscillator 315 of thePMIC 300 is running at up to 5 MHz or even up to 105 Mhz, a highbandwidth rectifier circuit is implemented in the PMIC 300. As will bedescribed below, sensing the RMS current within an H bridge of thebridge IC 301 forms part of a feedback loop which enables the driverdevice 202 to drive the ultrasonic transducer 215 with high precision.The feedback loop is a game changer in the industry of drivingultrasound transducers since it accommodates for any process variationin the piezo electric transducer production (variations of resonancefrequencies) and it compensates for temperature effects of the resonancefrequency. This is achieved, in part, by the inventive realisation ofintegrating the ADC 318, the oscillator 315 and the DLL within the sameintegrated circuit of the PMIC 300. The integration enables thesesub-systems to communicate with one another at high speed (e.g. at theclock frequency of 5 MHz or up to 105 MHz). Reducing the lag betweenthese subsystems is a game changer in the ultrasonics industry,particularly in the field of mist generator devices.

The ADC 318 comprises a battery voltage monitoring input VBAT and acharger input voltage monitoring input VCHG as well as voltagemonitoring inputs VMON and VRTH as well as a temperature monitoringinput TEMP.

The temperature monitoring input TEMP receives a temperature signal fromthe temperature sensor 314 which is embedded within the PMIC 300. Thisenables the PMIC 300 to sense the actual temperature within the PMIC 300accurately so that the PMIC 300 can detect any malfunction within thePMIC 300 as well as malfunction to other components on the printedcircuit board which affect the temperature of the PMIC 300. The PMIC 300can then control the bridge IC 301 to prevent excitation of theultrasonic transducer 215 if there is a malfunction in order to maintainthe safety of the mist inhaler device 200.

The additional temperature sensor input VRTH receives a temperaturesensing signal from an external temperature sensor within the driverdevice 202 which monitors the temperature of the battery 250. The PMIC300 can thus react to stop the battery 250 from being charged in theevent of a high battery temperature or otherwise shut down the driverdevice 202 in order to reduce the risk of damage being caused by anexcessively high battery temperature.

The PMIC 300 comprises an LED driver 320 which, in this example,receives a digital drive signal from the digital core 316 and providesLED drive output signals to six LEDs 321-326 which are configured to becoupled to output pins of the PMIC 300. The LED driver 320 can thusdrive and dim the LEDs 321-326 in up to six independent channels.

The PMIC 300 comprises a first digital to analogue converter (DAC) 327which converts digital signals within the PMIC 300 into an analoguevoltage control signal which is output from the PMIC 300 via an outputpin VDAC0. The first DAC 327 converts a digital control signal generatedby the digital core 316 into an analogue voltage control signal which isoutput via the output pin VDAC0 to control a voltage regulator circuit,such as the boost converter 305. The voltage control signal thuscontrols the voltage regulator circuit to generate a predeterminedvoltage for modulation by the H-bridge circuit to drive a resonantcircuit, such as the ultrasonic transducer 215, in response to feedbacksignals which are indicative of the operation of the resonant circuit(the ultrasonic transducer 215).

In this example, the PMIC 300 comprises a second DAC 328 which convertsdigital signals within the PMIC 300 into an analogue signal which isoutput from the PMIC 300 via a second analogue output pin VDAC1.

Embedding the DACs 327, 328 within the same microchip as the othersubsystems of the PMIC 300 allows the DACs 327, 328 to communicate withthe digital core 316 and other components within the PMIC 300 at highspeed with no or minimal communication lag. The DACs 327, 328 provideanalogue outputs which control external feedback loops. For instance,the first DAC 327 provides the control signal VCTL to the boostconverter 305 to control the operation of the boost converter 305. Inother examples, the DACs 327, 328 are configured to provide a drivesignal to a DC-DC buck converter instead of or in addition to the boostconverter 305. Integrating the two independent DAC channels in the PMIC300 enables the PMIC 300 to manipulate the feedback loop of anyregulator used in the driver device 202 and allows the driver device 202to regulate the sonication power of the ultrasonic transducer 215 or toset analogue thresholds for absolute maximum current and temperaturesettings of the ultrasonic transducer 215.

The PMIC 300 comprises a serial communication interface which, in thisexample, is an I2C interface which incorporates external I2C address setthrough pins.

The PMIC 300 also comprises various functional blocks which include adigital machine (FSM) to implement the functionality of the microchip.These blocks will be described in more detail below.

Referring now to FIG. 45 of the accompanying drawings, a pulse widthmodulation (PWM) signal generator subsystem 329 is embedded within thePMIC 300. The PWM generator system 329 comprises the oscillator 315, andfrequency divider 330, a multiplexer 331 and a delay locked loop (DLL)332. As will be described below, the PWM generator system 329 is a twophase centre aligned PWM generator.

The frequency divider 330, the multiplexer 331 and the DLL 332 areimplemented in digital logic components (e.g. transistors, logic gates,etc.) within the digital core 316.

In examples of this disclosure, the frequency range which is covered bythe oscillator 315 and respectively by the PWM generator system 329 is50 kHz to 5 MHz or up to 105 MHz. The frequency accuracy of the PWMgenerator system 329 is ±1% and the spread over temperature is ±1%. Inthe IC market today, no IC has an embedded oscillator and two phasecentre aligned PWM generator that can provide a frequency range of 50kHz to 5 MHz or up to 105 MHz.

The oscillator 315 generates a main clock signal (clk_m) with afrequency of 50 kHz to 5 MHz or up to 105 MHz. The main clock clk_m isinput to the frequency divider 330 which divides the frequency of themain clock clk_m by one or more predetermined divisor amounts. In thisexample, the frequency divider 330 divides the frequency of the mainclock clk_m by 2, 4, 8 and 16 and provides the divided frequency clocksas outputs to the multiplexer 331. The multiplexer 331 multiplexes thedivided frequency clocks and provides a divided frequency output to theDLL 332. This signal which is passed to the DLL 332 is a frequencyreference signal which controls the DLL 332 to output signals at adesired frequency. In other examples, the frequency divider 330 and themultiplexer 331 are omitted.

The oscillator 315 also generates two phases; a first phase clock signalPhase 1 and a second phase clock signal Phase 2. The phases of the firstphase clock signal and the second phase clock signal are centre aligned.As illustrated in FIG. 46 :

-   -   The first phase clock signal Phase 1 is high for a variable time        of clk_m's positive half-period and low during clk_m's negative        half-period.    -   The second phase clock signal Phase 2 is high for a variable        time of clk_m's negative half-period and low during clk_m's        positive half-period.

Phase 1 and Phase 2 are then sent to the DLL 332 which generates adouble frequency clock signal using the first phase clock signal Phase 1and the second phase clock signal Phase 2. The double frequency clocksignal is double the frequency of the main clock signal clk_m. In thisexample, an “OR” gate within the DLL 332 generates the double frequencyclock signal using the first phase clock signal Phase 1 and the secondphase clock signal Phase 2. This double frequency clock or the dividedfrequency coming from the frequency divider 330 is selected based on atarget frequency selected and then used as reference for the DLL 332.

Within the DLL 332, a signal referred to hereafter as “clock” representsthe main clock clk_m multiplied by 2, while a signal referred tohereafter as “clock_del” is a replica of clock delayed by one period ofthe frequency. Clock and clock_del are passed through a phase frequencydetector. A node Vc is then charged or discharged by a charge-pump basedon the phase error polarity. A control voltage is fed directly tocontrol the delay of every single delay unit within the DLL 332 untilthe total delay of the DLL 332 is exactly one period.

The DLL 332 controls the rising edge of the first phase clock signalPhase 1 and the second phase clock signal Phase 2 to be synchronous withthe rising edge of the double frequency clock signal. The DLL 332adjusts the frequency and the duty cycle of the first phase clock signalPhase 1 and the second phase clock signal Phase 2 in response to arespective frequency reference signal and a duty cycle control signal toproduce a first phase output signal Phase A and a second phase outputsignal Phase B to drive an H-bridge or an inverter to generate an ACdrive signal to drive an ultrasonic transducer.

The PMIC 300 comprises a first phase output signal terminal PHASE_Awhich outputs the first phase output signal Phase A to an H-bridgecircuit and a second phase output signal terminal PHASE_B which outputsthe second phase output signal Phase B to an H-bridge circuit.

In this example, the DLL 332 adjusts the duty cycle of the first phaseclock signal Phase 1 and the second phase clock signal Phase 2 inresponse to the duty cycle control signal by varying the delay of eachdelay line in the DLL 332 response to the duty cycle control signal.

The clock is used at double of its frequency because guarantees betteraccuracy. As shown in FIG. 47 , for the purpose of explanation if thefrequency of the main clock clk_m is used (which it is not in examplesof this disclosure), Phase A is synchronous with clock's rising edge R,while Phase B is synchronous with clock's falling edge F. The delay lineof the DLL 332 controls the rising edge R and so, for the falling edgeF, the PWM generator system 329 would need to rely on a perfect matchingof the delay units of the DLL 332 which can be imperfect. However, toremove this error, the PWM generator system 329 uses the doublefrequency clock so that both Phase A and Phase B are synchronous withthe rising edge R of the double frequency clock.

To perform a duty-cycle from 20% to 50% with a 2% step size, the delayline of the DLL 332 comprises 25 delay units, with the output of eachrespective delay unit representing a Phase nth. Eventually the phase ofthe output of the final delay unit will correspond to the input clock.Considering that all delays will be almost the same, a particular dutycycle is obtained with the output of the specific delay unit with simplelogic in the digital core 316.

It is important to take care of the DLL 332 startup as the DLL 332 mightnot be able to lock a period of delay but two or more periods, takingthe DLL 332 to a non-convergence zone. To avoid this issue, a start-upcircuit is implemented in the PWM generator system 329 which allows theDLL 332 to start from a known and deterministic condition. The start-upcircuit furthermore allows the DLL 332 to start with the minimum delay.

In examples of this disclosure, the frequency range covered by the PWMgenerator system 329 is extended and so the delay units in the DLL 332can provide delays of 4 ns (for an oscillator frequency of 5 MHz) to 400ns (for an oscillator frequency of 50 kHz). In order to accommodate forthese differing delays, capacitors Cb are included in the PWM generatorsystem 329, with the capacitor value being selected to provide therequired delay.

The Phase A and Phase B are output from the DLL 332 and passed through adigital IO to the bridge IC 301 so that the Phase A and Phase B can beused to control the operation of the bridge IC 301.

The battery charging functionality of the driver device 202 will now bedescribed in more detail. The battery charging sub-system comprises thecharger circuit 317 which is embedded in the PMIC 300 and controlled bya digital charge controller hosted in the PMIC 300. The charger circuit317 is controlled by the microcontroller 303 via the communication bus302. The battery charging sub-system is able to charge a single celllithium polymer (LiPo) or lithium-ion (Li-ion) battery, such as thebattery 250 described above.

In this example, the battery charging sub-system is able to charge abattery or batteries with a charging current of up to 1 A from a 5Vpower supply (e.g. a USB power supply). One or more of the followingparameters can be programmed through the communication bus 302 (I2Cinterface) to adapt the charge parameters for the battery:

-   -   Charge voltage can be set between 3.9V and 4.3V in 100 mV steps.    -   The charge current can be set between 150 mA and 1000 mA in 50        mA steps.    -   The pre-charge current is 1/10 of the charge current.    -   Pre-charge and fast charge timeouts can be set between 5 and 85        min respectively 20 and 340 min.    -   Optionally an external negative temperature coefficient (NTC)        thermistor can be used to monitor the battery temperature.

In some examples, the battery charging sub-system reports one or more ofthe following events by raising an interrupt to the host microcontroller303:

-   -   Battery detected    -   Battery is being charged    -   Battery is fully charged    -   Battery is not present    -   Charge timeout reached    -   Charging supply is below the undervoltage limit

The main advantage of having the charger circuit 317 embedded in thePMIC 300, is that it allows all the programming options and eventindications listed to be implemented within the PMIC 300 whichguarantees the safe operation of the battery charging sub-system.Furthermore, a significant manufacturing cost and PCB space saving canbe accomplished compared with conventional mist inhaler devices whichcomprise discrete components of a charging system mounted separately ona PCB. The charger circuit 317 also allows for highly versatile settingof charge current and voltage, different fault timeouts and numerousevent flags for detailed status analysis.

The analogue to digital converter (ADC) 318 will now be described inmore detail. The inventors had to overcome significant technicalchallenges to integrate the ADC 318 within the PMIC 300 with the highspeed oscillator 315. Moreover, integrating the ADC 318 within the PMIC300 goes against the conventional approach in the art which relies onusing one of the many discrete ADC devices that are available in the ICmarket.

In this example, the ADC 318 samples at least one parameter within theultrasonic transducer driver chip (PMIC 300) at a sampling rate which isequal to the frequency of the main clock signal clk_m. In this example,the ADC 318 is a 10 bit analogue to digital converter which is able tounload digital sampling from the microprocessor 303 to save theresources of the microprocessor 303. Integrating the ADC 318 within thePMIC 300 also avoids the need to use an I2C bus that would otherwiseslow down the sampling ability of the ADC (a conventional device relieson an I2C bus to communicate data between a dedicated discrete ADC and amicrocontroller at a limited clock speed of typically up to 400 kHz).

In examples of this disclosure, one or more of the following parameterscan be sampled sequentially by the ADC 318:

-   -   i. An rms current signal which is received at the ultrasonic        transducer driver chip (PMIC 300) from an external inverter        circuit which is driving an ultrasonic transducer. In this is        example, this parameter is a root mean square (rms) current        reported by the bridge IC 301. Sensing the rms current is        important to implementing the feedback loop used for driving the        ultrasound transducer 215. The ADC 318 is able to sense the rms        current directly from the bridge IC 301 via a signal with        minimal or no lag since the ADC 318 does not rely on this        information being transmitted via an I2C bus. This provides a        significant speed and accuracy benefit over conventional devices        which are constrained by the comparatively low speeds of an I2C        bus.    -   ii. The voltage of a battery connected to the PMIC 300.    -   iii. The voltage of a charger connected to the PMIC 300.    -   iv. A temperature signal, such as a temperature signal which is        indicative of the PMIC 300 chip temperature. As described above,        this temperature can be measured very accurately due to the        temperature sensor 314 being embedded in the same IC as the        oscillator 315. For example, if the PMIC 300 temperature goes        up, the current, frequency and PWM are regulated by the PMIC 300        to control the transducer oscillation which in turn controls the        temperature.    -   v. Two external pins.    -   vi. External NTC temperature sensor to monitor battery pack        temperature.

In some examples, the ADC 318 samples one or more of the above-mentionedsources sequentially, for instance in a round robin scheme. The ADC 318samples the sources at high speed, such as the speed of the oscillator315 which may be up to 5 MHz or up to 105 MHz.

In some examples, the device 202 is configured so that a user or themanufacturer of the device can specify how many samples shall be takenfrom each source for averaging. For instance, a user can configure thesystem to take 512 samples from the rms current input, 64 samples fromthe battery voltage, 64 from the charger input voltage, 32 samples fromthe external pins and 8 from the NTC pin. Furthermore, the user can alsospecify if one of the above-mentioned sources shall be skipped.

In some examples, for each source the user can specify two digitalthresholds which divide the full range into a plurality of zones, suchas 3 zones. Subsequently the user can set the system to release aninterrupt when the sampled value changes zones e.g. from a zone 2 to azone 3.

No conventional IC available in the market today can perform the abovefeatures of the PMIC 300. Sampling with such flexibility and granularityis paramount when driving a resonant circuit or component, such as anultrasound transducer.

In this example, the PMIC 300 comprises an 8 bit general purpose digitalinput output port (GPIO). Each port can be configured as digital inputand digital output. Some of the ports have an analogue input function,as shown in the table in FIG. 48 .

The GPIO7-GPIO5 ports of the PMIC 300 can be used to set the device'saddress on the communication (I2C) bus 302. Subsequently eight identicaldevices can be used on the same I2C bus. This is a unique feature in theIC industry since it allows eight identical devices to be used on thesame I2C bus without any conflicting addresses. This is implemented byeach device reading the state of GPIO7-GPIO5 during the first 100 μsafter the startup of the PMIC 300 and storing that portion of theaddress internally in the PMIC 300. After the PMIC 300 has been startedup the GPIOs can be used for any other purpose.

As described above, the PMIC 300 comprises a six channel LED driver 320.In this example the LED driver 320 comprises N-Channel Metal-OxideSemiconductor (NMOS) current sources which are 5V tolerant. The LEDdriver 320 is configured to set the LED current in four discrete levels;5 mA, 10 mA, 15 mA and 20 mA. The LED driver 320 is configured to dimeach LED channel with a 12 bit PWM signal either with or without gammacorrection. The LED driver 320 is configured to vary the PWM frequencyfrom 300 Hz to 1.5 KHz. This feature is unique in the field ofultrasonic mist inhaler devices as the functionality is embedded as asub-system of the PMIC 300.

In this example, the PMIC 300 comprises two independent 6 Bit Digital toAnalog Converters (DAC) 327, 328 which are incorporated into the PMIC300. The purpose of the DACs 327, 328 is to output an analogue voltageto manipulate the feedback path of an external regulator (e.g. the DC-DCBoost converter 305 a Buck converter or a LDO). Furthermore, in someexamples, the DACs 327, 328 can also be used to dynamically adjust theover current shutdown level of the bridge IC 301, as described below.

The output voltage of each DAC 327, 328 is programmable between 0V and1.5V or between 0V and V_battery (Vbat). In this example, the control ofthe DAC output voltage is done via I2C commands. Having two DACincorporated in the PMIC 300 is unique and will allow the dynamicmonitoring control of the current. If either DAC 327, 328 was anexternal chip, the speed would fall under the same restrictions of speedlimitations due to the I2C protocol. The active power monitoringarrangement of the device 202 works with optimum efficiency if all theseembedded features are in the PMIC. Had they been external components,the active power monitoring arrangement would be totally inefficient.

Referring now to FIG. 49 of the accompanying drawings, the bridge IC 301is a microchip which comprises an embedded power switching circuit 333.In this example, the power switching circuit 333 is an H-bridge 334which is shown in FIG. 50 and which is described in detail below. It is,however, to be appreciated that the bridge IC 301 of other examples mayincorporate an alternative power switching circuit to the H-bridge 334,provided that the power switching circuit performs an equivalentfunction for generating an AC drive signal to drive the ultrasonictransducer 215.

The bridge IC 301 comprises a first phase terminal PHASE A whichreceives a first phase output signal Phase A from the PWM signalgenerator subsystem of the PMIC 300. The bridge IC 301 also comprises asecond phase terminal PHASE B which receives a second phase outputsignal Phase B from the PWM signal generator subsystem of the PMIC 300.

The bridge IC 301 comprises a current sensing circuit 335 which sensescurrent flow in the H-bridge 334 directly and provides an RMS currentoutput signal via the RMS_CURR pin of the bridge IC 301. The currentsensing circuit 335 is configured for over current monitoring, to detectwhen the current flowing in the H-bridge 334 is above a predeterminedthreshold. The integration of the power switching circuit 333 comprisingthe H-bridge 334 and the current sensing circuit 335 all within the sameembedded circuit of the bridge IC 301 is a unique combination in the ICmarket. At present, no other integrated circuit in the IC marketcomprises an H-bridge with embedded circuitry for sensing the RMScurrent flowing through the H-bridge.

The bridge IC 301 comprises a temperature sensor 336 which includes overtemperature monitoring. The temperature sensor 336 is configured to shutdown the bridge IC 301 or disable at least part of the bridge IC 336 inthe event that the temperature sensor 336 detects that the bridge IC 301is operating at a temperature above a predetermined threshold. Thetemperature sensor 336 therefore provides an integrated safety functionwhich prevents damage to the bridge IC 301 or other components withinthe driver device 202 in the event that the bridge IC 301 operates at anexcessively high temperature.

The bridge IC 301 comprises a digital state machine 337 which isintegrally connected to the power switching circuit 333. The digitalstate machine 337 receives the phase A and phase B signals from the PMIC300 and an ENABLE signal, for instance from the microcontroller 303. Thedigital state machine 337 generates timing signals based on the firstphase output signal Phase A and the second phase output signal Phase B.

The digital state machine 337 outputs timing signals corresponding tothe phase A and phase B signals as well as a BRIDGE_PR and BRIDGE_ENsignals to the power switching circuit 333 in order to control the powerswitching circuit 333. The digital state machine 337 thus outputs thetiming signals to the switches T₁-T₄ of the H-bridge circuit 334 tocontrol the switches T₁-T₄ to turn on and off in a sequence such thatthe H-bridge circuit outputs an AC drive signal for driving a resonantcircuit, such as the ultrasonic transducer 215.

As described in more detail below, the switching sequence comprises afree-float period in which the first switch T₁ and the second switch T₂are turned off and the third switch T₃ and the fourth switch T₄ areturned on in order to dissipate energy stored by the resonant circuit(the ultrasonic transducer 215).

The bridge IC 301 comprises a test controller 338 which enables thebridge IC 301 to be tested to determine whether the embedded componentswithin the bridge IC 301 are operating correctly. The test controller338 is coupled to TEST_DATA, TEST_CLK and TEST_LOAD pins so that thebridge IC 301 can be connected to an external control device which feedsdata into and out from the bridge IC 301 to test the operation of thebridge IC 301. The bridge IC 301 also comprises a TEST BUS which enablesthe digital communication bus within the bridge IC 301 to be tested viaa TST_PAD pin.

The bridge IC 301 comprises a power on reset circuit (POR) 339 whichcontrols the startup operation of the bridge IC 301. The POR 339 ensuresthat the bridge IC 301 starts up properly only if the supply voltage iswithin a predetermined range. If the power supply voltage is outside ofthe predetermined range, for instance if the power supply voltage is toohigh, the POR 339 delays the startup of the bridge IC 301 until thesupply voltage is within the predetermined range.

The bridge IC 301 comprises a reference block (BG) 340 which provides aprecise reference voltage for use by the other subsystems of the bridgeIC 301.

The bridge IC 301 comprises a current reference 341 which provides aprecise current to the power switching circuit 333 and/or othersubsystems within the bridge IC 301, such as the current sensor 335.

The temperature sensor 336 monitors the temperature of the silicon ofthe bridge IC 301 continuously. If the temperature exceeds thepredetermined temperature threshold, the power switching circuit 333 isswitched off automatically. In addition, the over temperature may bereported to an external host to inform the external host that an overtemperature event has occurred.

The digital state machine (FSM) 337 generates the timing signals for thepower switching circuit 333 which, in this example, are timing signalsfor controlling the H-bridge 334.

The bridge IC 301 comprises comparators 342, 343 which compare signalsfrom the various subsystems of the bridge IC 301 with the voltage andcurrent references 340, 341 and provide reference output signals via thepins of the bridge IC 301.

Referring again to FIG. 50 of the accompanying drawings, the H-bridge334 of this example comprises four switches in the form of NMOS fieldeffect transistors (FET) switches on both sides of the H-bridge 334. TheH-bridge 334 comprises four switches or transistors T₁-T₄ which areconnected in an H-bridge configuration, with each transistor T₁-T₄ beingdriven by a respective logic input A-D. The transistors T₁-T₄ areconfigured to be driven by a bootstrap voltage which is generatedinternally with two external capacitors Cb which are connected asillustrated in FIG. 50 .

The H-bridge 334 comprises various power inputs and outputs which areconnected to the respective pins of the bridge IC 301. The H-bridge 334receives the programmable voltage VBOOST which is output from the boostconverter 305 via a first power supply terminal, labelled VBOOST in FIG.50 . The H-bridge 334 comprises a second power supply terminal, labelledVSS_P in FIG. 50 .

The H-bridge 334 comprises outputs OUTP, OUTN which are configured toconnect to respective terminals of the ultrasonic transducer 215 so thatthe AC drive signal output from the H-bridge 334 can drive theultrasonic transducer 215.

The switching of the four switches or transistors T₁-T₄ is controlled byswitching signals from the digital state machine 337 via the logic inputA-D. It is to be appreciated that, while FIG. 50 shows four transistorsT₁-T₄, in other examples, the H-bridge 334 incorporates a larger numberof transistors or other switching components to implement thefunctionality of the H-bridge.

In this example, the H-bridge 334 operates at a switching power of 22 Wto 50 W in order to deliver an AC drive signal with sufficient power todrive the ultrasonic transducer 215 to generate mist optimally. Thevoltage which is switched by the H-bridge 334 of this example is ±15 V.In other examples, the voltage is ±20 V.

In this example, the H-bridge 334 switches at a frequency of 3 MHz to 5MHz or up to 105 MHz. This is a high switching speed compared withconventional integrated circuit H-bridges which are available in the ICmarket. For instance, a conventional integrated circuit H-bridgeavailable in the IC market today is configured to operate at a maximumfrequency of only 2 MHz. Aside from the bridge IC 301 described herein,no conventional integrated circuit H-bridge available in the IC marketis able to operate at a power of 22 V to 50 V at a frequency of up to 5MHz, let alone up to 105 MHz.

Referring now to FIG. 51 of the accompanying drawings, the currentsensor 335 comprises positive and negative current sense resistorsRshuntP, RshuntN which are connected in series with the respective highand low sides of the H-bridge 334, as shown in FIG. 50 . The currentsense resistors RshuntP, RshuntN are low value resistors which, in thisexample, are 0.1Ω. The current sensor 335 comprises a first voltagesensor in the form of a first operational amplifier 344 which measuresthe voltage drop across the first current sensor resistor RshuntP and asecond voltage sensor in the form of a second operational amplifier 345which measures the voltage drop across the second current sensorresistor RshuntN. In this example, the gain of each operationalamplifier 344, 345 is 2V/V. The output of each operational amplifier344, 345 is, in this example, 1 mA/V. The current sensor 335 comprises apull down resistor Ra which, in this example, is 2 kΩ. The outputs ofthe operational amplifiers 344, 345 provide an output CSout which passesthrough a low pass filter 346 which removes transients in the signalCSout. An output Vout of the low pass filter 346 is the output signal ofthe current sensor 335.

The current sensor 335 thus measures the AC current flowing through theH-bridge 334 and respectively through the ultrasonic transducer 215. Thecurrent sensor 335 translates the AC current into an equivalent RMSoutput voltage (Vout) relative to ground. The current sensor 335 hashigh bandwidth capability since the H-bridge 334 can be operated at afrequency of up to 5 MHz or, in some examples, up to 105 MHz. The outputVout of the current sensor 335 reports a positive voltage which isequivalent to the measured AC rms current flowing through the ultrasonictransducer 215. The output voltage Vout of the current sensor 335 is, inthis example, fed back to the control circuitry within the bridge IC 301to enable the bridge IC 301 to shut down the H-bridge 334 in the eventthat the current flowing through the H-bridge 334 and hence through thetransducer 215 is in excess of a predetermined threshold. In addition,the over current threshold event is reported to the first comparator 342in the bridge IC 301 so that the bridge IC 301 can report the overcurrent event via the OVC_TRIGG pin of the bridge IC 301.

Referring now to FIG. 52 of the accompanying drawings, the control ofthe H-bridge 334 will now be described also with reference to theequivalent piezoelectric model of the ultrasonic transducer 215.

To develop a positive voltage across the outputs OUTP, OUTN of theH-bridge 334 as indicated by V_out in FIG. 52 (note the direction of thearrow) the switching sequence of the transistors T₁-T₄ via the inputsA-D is as follows:

-   -   1. Positive output voltage across the ultrasonic transducer 215:        A-ON, B-OFF, C-OFF, D-ON    -   2. Transition from positive output voltage to zero: A-OFF,        B-OFF, C-OFF, D-ON. During this transition, C is switched off        first to minimise or avoid power loss by minimising or avoiding        current flowing through A and C if there is a switching error or        delay in A.    -   3. Zero output voltage: A-OFF, B-OFF, C-ON, D-ON. During this        zero output voltage phase, the terminals of the outputs OUTP,        OUTN of the H-bridge 334 are grounded by the C and D switches        which remain on. This dissipates the energy stored by the        capacitors in the equivalent circuit of the ultrasonic        transducer, which minimises the voltage overshoot in the        switching waveform voltage which is applied to the ultrasonic        transducer.    -   4. Transition from zero to negative output voltage: A-OFF,        B-OFF, C-ON, D-OFF.    -   5. Negative output voltage across the ultrasonic transducer 215:        A-OFF, B-ON, C-ON, D-OFF

At high frequencies of up to 5 MHz or even up to 105 MHz, it will beappreciated that the time for each part of the switching sequence isvery short and in the order of nanoseconds or picoseconds. For instance,at a switching frequency of 6 MHz, each part of the switching sequenceoccurs in approximately 80 ns.

A graph showing the output voltage OUTP, OUTN of the H-bridge 334according to the above switching sequence is shown in FIG. 53 of theaccompanying drawings. The zero output voltage portion of the switchingsequence is included to accommodate for the energy stored by theultrasonic transducer 215 (e.g. the energy stored by the capacitors inthe equivalent circuit of the ultrasonic transducer). As describedabove, this minimises the voltage overshoot in the switching waveformvoltage which is applied to the ultrasonic transducer and henceminimises unnecessary power dissipation and heating in the ultrasonictransducer.

Minimising or removing voltage overshoot also reduces the risk of damageto transistors in the bridge IC 301 by preventing the transistors frombeing subject to voltages in excess of their rated voltage. Furthermore,the minimisation or removal of the voltage overshoot enables the bridgeIC 301 to drive the ultrasonic transducer accurately in a way whichminimises disruption to the current sense feedback loop describedherein. Consequently, the bridge IC 301 is able to drive the ultrasonictransducer at a high power of 22 W to 50 W or even as high as 70 W at ahigh frequency of up to 5 MHz or even up to 105 MHz.

The bridge IC 301 of this example is configured to be controlled by thePMIC 300 to operate in two different modes, referred to herein as aforced mode and a native frequency mode. These two modes of operationare novel over existing bridge ICs. In particular, the native frequencymode is a major innovation which offers substantial benefits in theaccuracy and efficiency of driving an ultrasonic transducer as comparedwith conventional devices.

Forced Frequency Mode (FFM)

In the forced frequency mode the H-bridge 334 is controlled in thesequence described above but at a user selectable frequency. As aconsequence, the H-bridge transistors T₁-T₄ are controlled in a forcedway irrespective of the inherent resonant frequency of the ultrasonictransducer 215 to switch the output voltage across the ultrasonictransducer 215. The forced frequency mode therefore allows the H-bridge334 to drive the ultrasonic transducer 215, which has a resonantfrequency f1, at different frequency f2.

Driving an ultrasonic transducer at a frequency which is different fromits resonant frequency may be appropriate in order to adapt theoperation to different applications. For example, it may be appropriateto drive an ultrasonic transducer at a frequency which is slightly offthe resonance frequency (for mechanical reasons to prevent mechanicaldamage to the transducer). Alternatively, it may be appropriate to drivean ultrasonic transducer at a low frequency but the ultrasonictransducer has, because of its size, a different native resonancefrequency.

The driver device 202 controls the bridge IC 301 to drive the ultrasonictransducer 215 in the forced frequency mode in response to theconfiguration of the driver device 202 for a particular application or aparticular ultrasonic transducer. For instance, the driver device 202may be configured to operate in the forced frequency mode when the mistinhaler device 200 is being used for a particular application, such asgenerating a mist from a liquid of a particular viscosity containing adrug for delivery to a user.

Native Frequency Mode (NFM)

The following native frequency mode of operation is a significantdevelopment and provides benefits in improved accuracy and efficiencyover conventional ultrasonic drivers that are available on the IC markettoday.

The native frequency mode of operation follows the same switchingsequence as described above but the timing of the zero output portion ofthe sequence is adjusted to minimise or avoid problems that can occurdue to current spikes in the forced frequency mode operation. Thesecurrent spikes occur when the voltage across the ultrasonic transducer215 is switched to its opposite voltage polarity. An ultrasonictransducer which comprises a piezoelectric crystal has an electricalequivalent circuit which incorporates a parallel connected capacitor(e.g. see the piezo model in FIG. 52 ). If the voltage across theultrasonic transducer is hard-switched from a positive voltage to anegative voltage, due to the high dV/dt there can be a large currentflow current flow as the energy stored in the capacitor dissipates.

The native frequency mode avoids hard switching the voltage across theultrasonic transducer 215 from a positive voltage to a negative voltage(and vice versa). Instead, prior to applying the reversed voltage, theultrasonic transducer 215 (piezoelectric crystal) is left free-floatingwith zero voltage applied across its terminals for a free-float period.The PMIC 300 sets the drive frequency of the bridge IC 301 such that thebridge 334 sets the free-float period such that current flow inside theultrasonic transducer 215 (due to the energy stored within thepiezoelectric crystal) reverses the voltage across the terminals of theultrasonic transducer 215 during the free-float period.

Consequently, when the H-bridge 334 applies the negative voltage at theterminals of the ultrasonic transducer 215 the ultrasonic transducer 215(the capacitor in the equivalent circuit) has already been reversecharged and no current spikes occur because there is no high dV/dt.

It is, however, to be appreciated that it takes time for the chargewithin the ultrasonic transducer 215 (piezoelectric crystal) to build upwhen the ultrasonic transducer 215 is first activated. Therefore, theideal situation in which the energy within the ultrasonic transducer 215is to reverse the voltage during the free-float period occurs only afterthe oscillation inside the ultrasonic transducer 215 has built up thecharge. To accommodate for this, when the bridge IC 301 activates theultrasonic transducer 215 for the first time, the PMIC 300 controls thepower delivered through the H-bridge 334 to the ultrasonic transducer215 to a first value which is a low value (e.g. 5 V). The PMIC 300 thencontrols the power delivered through the H-bridge 334 to the ultrasonictransducer 215 to increase over a period of time to a second value (e.g.15 V) which is higher than the first value in order to build up theenergy stored within the ultrasonic transducer 215. Current spikes stilloccur during this ramp of the oscillation until the current inside theultrasonic transducer 215 developed sufficiently. However, by using alow first voltage at start up those current spikes are kept sufficientlylow to minimise the impact on the operation of the ultrasonic transducer215.

In order to implement the native frequency mode, the driver device 202controls the frequency of the oscillator 315 and the duty cycle (ratioof turn-on time to free-float time) of the AC drive signal output fromthe H-bridge 334 with high precision. In this example, the driver device202 performs three control loops to regulate the oscillator frequencyand the duty cycle such that the voltage reversal at the terminals ofthe ultrasonic transducer 215 is as precise as possible and currentspikes are minimised or avoided as far as possible. The precise controlof the oscillator and the duty cycle using the control loops is asignificant advance in the field of IC ultrasonic drivers.

During the native frequency mode of operation, the current sensor 335senses the current flowing through the ultrasonic transducer 215(resonant circuit) during the free-float period. The digital statemachine 337 adapts the timing signals to switch on either the firstswitch T₁ or the second switch T₂ when the current sensor 335 sensesthat the current flowing through the ultrasonic transducer 215 (resonantcircuit) during the free-float period is zero.

FIG. 54 of the accompanying drawings shows the oscillator voltagewaveform 347 (V(osc)), a switching waveform 348 resulting from theturn-on and turn-off the left hand side high switch T₁ of the H-bridge334 and a switching waveform 349 resulting from the turn-on and turn-offthe right hand side high switch T₂ of the H-bridge 334. For anintervening free-float period 350, both high switches T₁, T₂ of theH-bridge 334 are turned off (free-floating phase). The duration of thefree-float period 350 is controlled by the magnitude of the free-floatcontrol voltage 351 (Vphioff).

FIG. 55 of the accompanying drawings shows the voltage waveform 352 at afirst terminal of the ultrasonic transducer 215 (the voltage waveform isreversed at the second terminal of the ultrasonic transducer 215) andthe piezo current 353 flowing through the ultrasonic transducer 215. Thepiezo current 353 represents an (almost) ideal sinusoidal waveform (thisis never possible in the forced frequency mode or in any bridge in theIC market).

Before the sinusoidal wave of the piezo current 353 reaches zero, theleft hand side high switch T₁ of the H-bridge 334 is turned off (here,the switch T₁ is turned off when the piezo current 353 is approximately6 A). The remaining piezo current 353 which flows within the ultrasonictransducer 215 due to the energy stored in the ultrasonic transducer 215(the capacitor of the piezo equivalent circuit) is responsible for thevoltage reversal during the free-float period 350. The piezo current 353decays to zero during the free-float period 350 and into negativecurrent flow domain thereafter. The terminal voltage at the ultrasonictransducer 215 drops from the supply voltage (in this case 19 V) to lessthan 2 V and the drop comes to a stop when the piezo current 353 reacheszero. This is the perfect time to turn on the low-side switch T₃ of theH-bridge 334 in order to minimise or avoid a current spike.

Compared to the forced frequency mode described above, the nativefrequency mode has at least three advantages:

-   -   1. The current spike associated with hard switching of the        package capacitor is significantly reduced or avoided        completely.    -   2. Power loss due to hard switching is almost eliminated.    -   3. Frequency is regulated by the control loops and will be kept        close to the resonance of the piezo crystal (i.e. the native        resonance frequency of the piezo crystal).

In the case of the frequency regulation by the control loops (advantage3 above), the PMIC 300 starts by controlling the bridge IC 301 to drivethe ultrasonic transducer 215 at a frequency above the resonance of thepiezo crystal. The PMIC 300 then controls the bridge IC 301 to that thefrequency of the AC drive signal decays/reduces during start up. As soonas the frequency approaches resonance frequency of the piezo crystal,the piezo current will develop/increase rapidly. Once the piezo currentis high enough to cause the desired voltage reversal, the frequencydecay/reduction is stopped by the PMIC 300. The control loops of thePMIC 300 then take over the regulation of frequency and duty cycle ofthe AC drive signal.

In the forced frequency mode, the power delivered to the ultrasonictransducer 215 is controlled through the duty cycle and/or a frequencyshift and/or by varying the supply voltage. However, in this example inthe native frequency mode the power delivered to the ultrasonictransducer 215 controlled only through the supply voltage.

In this example, during a setup phase of operation of the driver device,the bridge IC 301 is configured to measure the length of time taken forthe current flowing through the ultrasonic transducer 215 (resonantcircuit) to fall to zero when the first switch T₁ and the second switchT₂ are turned off and the third switch T₃ and the fourth switch T₄ areturned on. The bridge IC 301 then sets the length of time of thefree-float period to be equal to the measured length of time.

Referring now to FIG. 56 of the accompanying drawings, the PMIC 300 andthe bridge IC 301 of this example are designed to work together as acompanion chip set. The PMIC 300 and the bridge IC 301 are connectedtogether electrically for communication with one another. In thisexample, there are interconnections between the PMIC 300 and the bridgeIC 301 which enable the following two categories of communication:

-   -   1. control signals    -   2. feedback signals

The connections between the PHASE_A and PHASE_B pins of the PMIC 300 andthe bridge IC 301 carry the PWM modulated control signals which drivethe H-bridge 334. The connection between the EN_BR pins of the PMIC 300and the bridge IC 301 carries the EN_BR control signal which triggersthe start of the H-bridge 334. The timing between the PHASE_A, PHASE_Band EN_BR control signals is important and handled by the digital bridgecontrol of the PMIC 300.

The connections between the CS, OC and OT pins of the PMIC 300 and thebridge IC 301 carry CS (current sense), OC (over current) and OT (overtemperature) feedback signals from the bridge IC 301 back to the PMIC300. Most notably, the CS (current sense) feedback signal comprises avoltage equivalent to the rms current flowing through the ultrasonictransducer 215 which is measured by the current sensor 335 of the bridgeIC 301.

The OC (over current) and OT (over temperature) feedback signals aredigital signals indicating that either an over current or an overvoltage event has been detected by the bridge IC 301. In this example,the thresholds for the over current and over temperature are set with anexternal resistor. Alternatively, the thresholds can also be dynamicallyset in response to signals passed to the OC_REF pin of the bridge IC 301from one of the two DAC channels VDAC0, VDAC1 from the PMIC 300.

In this example, the design of the PMIC 300 and the bridge IC 301 allowthe pins of these two integrated circuits to be connected directly toone another (e.g. via copper tracks on a PCB) so that there is minimalor no lag in the communication of signals between the PMIC 300 and thebridge IC 301. This provides a significant speed advantage overconventional bridges in the IC market which are typically controlled bysignals via a digital communications bus. For example, a standard I2Cbus is clocked at only 400 kHz, which is too slow for communicating datasampled at the high clock speeds of up to 5 MHz of examples of thisdisclosure.

While examples of this disclosure have been described above in relationto the microchip hardware, it is to be appreciated that other examplesof this disclosure comprise a method of operating the components andsubsystems of each microchip to perform the functions described herein.For instance, the methods of operating the PMIC 300 and the bridge IC301 in either the forced frequency mode or the native frequency mode.

Referring now to FIG. 57 of the accompanying drawings, the OTP IC 242comprises a power on reset circuit (POR) 354, a bandgap reference (BG)355, a cap-less low dropout regulator (LDO) 356, a communication (e.g.I2C) interface 357, a one-time programmable memory bank (eFuse) 358, anoscillator 359 and a general purpose input-output interface 360. The OTPIC 242 also comprises a digital core 361 which includes a cryptographicauthenticator. In this example, the cryptographic authenticator uses theElliptic Curve Digital Signature Algorithm (ECDSA) forencrypting/decrypting data stored within the OTP IC 242 as well as datatransmitted to and from the OTP IC 242.

The POR 354 ensures that the OTP IC 242 starts up properly only if thesupply voltage is within a predetermined range. If the supply voltage isoutside the predetermined range, the POR 354 resets the OTP IC 242 andwaits until the supply voltage is within the predetermined range.

The BG 355 provides precise reference voltages and currents to the LDO356 and to the oscillator 359. The LDO 356 supplies the digital core361, the communication interface 357 and the eFuse memory bank 358.

The OTP IC 242 is configured to operate in at least the following modes:

-   -   Fuse Programming (Fusing): During efuse programming (programming        of the one time programmable memory) a high current is required        to burn the relevant fuses within the eFuse memory bank 358. In        this mode higher bias currents are provided to maintain gain and        bandwidth of the regulation loop.    -   Fuse Reading: In this mode a medium level current is required to        maintain efuse reading within the eFuse memory bank 358. This        mode is executed during the startup of the OTP IC 242 to        transfer the content of the fuses to shadow registers. In this        mode the gain and bandwidth of the regulation loop is set to a        lower value than in the Fusing Mode.    -   Normal Operation: In this mode the LDO 356 is driven in a very        low bias current condition to operate the OTP IC 242 with low        power so that the OTP IC 242 consumes as little power as        possible.

The oscillator 359 provides the required clock for the digitalcore/engine 361 during testing (SCAN Test), during fusing and duringnormal operation. The oscillator 359 is trimmed to cope with the stricttiming requirements during the fusing mode.

In this example, the communication interface 357 is compliant with theFM+ specification of the I2C standard but it also complies with slow andfast mode. The OTP IC 242 uses the communication interface 357 tocommunicate with the driver device 202 (the Host) for data and keyexchange.

The digital core 361 implements the control and communicationfunctionality of the OTP IC 242. The cryptographic authenticator of thedigital core 361 enables the OTP IC 242 to authenticate itself (e.g.using ECDSA encrypted messages) with the driver device 202 (e.g. for aparticular application) to ensure that the OTP IC 242 is genuine andthat the OTP IC 242 is authorised to connect to the driver device 202(or another product).

With reference to FIG. 58 of the accompanying drawings, the OTP IC 242performs the following PKI procedure in order to authenticate the OTP IC242 for use with a Host (e.g. the driver device 202):

-   -   1. Verify Signer Public Key: The Host requests the Manufacturing        Public key and Certificate. The Host verifies the certificate        with the Authority Public key.    -   2. Verify Device Public Key: If the verification is successful,        the Host requests the Device Public key and Certificate. The        Host verifies the certificate with the Manufacturing Public key.    -   3. Challenge—Response: If the verification is successful, the        Host creates a random number challenge and sends it to the        Device. The End Product signs the random number challenge with        the Device Private key.    -   4. The signature is sent back to the Host for verification using        the Device Public key.

If all steps of the authentication procedure complete successfully thenthe Chain of Trust has been verified back to the Root of Trust and theOTP IC 242 is successfully authenticated for use with the Host. However,if any of the steps of the authentication procedure fail then the OTP IC242 is not authenticated for use with the Host and use of the deviceincorporating the OTP IC 242 is restricted or prevented.

The driver device comprises an AC driver for converting a voltage fromthe battery into an AC drive signal at a predetermined frequency todrive the ultrasonic transducer.

The driver device comprises an active power monitoring arrangement formonitoring the active power used by the ultrasonic transducer (asdescribed above) when the ultrasonic transducer is driven by the ACdrive signal. The active power monitoring arrangement provides amonitoring signal which is indicative of an active power used by theultrasonic transducer.

The processor within the driver device controls the AC driver andreceives the monitoring signal drive from the active power monitoringarrangement.

The memory of driver device stores instructions which, when executed bythe processor, cause the processor to:

-   -   A. control the AC driver to output an AC drive signal to the        ultrasonic transducer at a predetermined sweep frequency;    -   B. calculate the active power being used by the ultrasonic        transducer based on the monitoring signal;    -   C. control the AC driver to modulate the AC drive signal to        maximise the active power being used by the ultrasonic        transducer;    -   D. store a record in the memory of the maximum active power used        by the ultrasonic transducer and the sweep frequency of the AC        drive signal;    -   E. repeat steps A-D for a predetermined number of iterations        with the sweep frequency incrementing or decrementing with each        iteration such that, after the predetermined number of        iterations has occurred, the sweep frequency has been        incremented or decremented from a start sweep frequency to an        end sweep frequency;    -   F. identify from the records stored in the memory the optimum        frequency for the AC drive signal which is the sweep frequency        of the AC drive signal at which a maximum active power is used        by the ultrasonic transducer; and    -   G. control the AC driver to output an AC drive signal to the        ultrasonic transducer at the optimum frequency to drive the        ultrasonic transducer to atomise a liquid.

In some examples, the active power monitoring arrangement comprises acurrent sensing arrangement for sensing a drive current of the AC drivesignal driving the ultrasonic transducer, wherein the active powermonitoring arrangement provides a monitoring signal which is indicativeof the sensed drive current.

In some examples, the current sensing arrangement comprises anAnalog-to-Digital Converter which converts the sensed drive current intoa digital signal for processing by the processor.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D above with thesweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 2960 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: repeat steps A-D above with thesweep frequency being incremented from a start sweep frequency of 2900kHz to an end sweep frequency of 3100 kHz.

In some examples, the memory stores instructions which, when executed bythe processor, cause the processor to: in step G, control the AC driverto output an AC drive signal to the ultrasonic transducer at frequencywhich is shifted by a predetermined shift amount from the optimumfrequency.

In some examples, the predetermined shift amount is between 1-10% of theoptimum frequency.

2. Control and Information (CI) Section

The Control and Information section comprises an external EEPROM fordata storage, LEDs for user indications, a pressure sensor for airflowdetection and a Bluetooth Low Energy (BLE) capable microcontroller forconstant monitoring and managing of the aerosolisation section.

The pressure sensor used in the device serves two purposes. The firstpurpose is to prevent unwanted and accidental start of the sonic engine(driving the ultrasonic transducer). This functionality is implementedin the processing arrangement of the device, but optimised for lowpower, to constantly measures environmental parameters such astemperature and ambient pressure with internal compensation andreference setting in order to accurately detect and categorise what iscalled a true inhalation.

Unlike all the other mist inhaler devices on the market, this solutionuses the strength of a micro-controller to allow the use of only onesensor.

The second purpose of the pressure sensor is to be able to monitor notonly the exact duration of the inhalations by the user for preciseinhalation volume measurement, but also to be able to determine thestrength of the user inhalation which is a critical information inmedical conditions both for proper prescription and health monitoring.All in all, we are able to completely draw the pressure profile of everyinhalation and anticipate the end of an inhalation for bothaerosolisation optimisation and medical data behaviour comprehension.

This was possible with the usage of a Bluetooth™ Low Energy (BLE)microcontroller. Indeed, this enables the setting to provide extremelyaccurate inhalation times, optimised aerosolisation, monitor numerousparameters to guarantee safe misting and prevent the use of non-genuinee-liquids or aerosol chambers and protect both the device againstover-heating risks and the user against over-misting in one shot unlikeany other products on the market.

The use of the BLE microcontroller allows over-the-air update tocontinuously provide improved software to users based on anonymised datacollection and trained AI for PZT modelling.

3. Power Management (PM) Section

The Power Management section is constituted by the 3.7V LiPo batterypath to a low dropout regulator (LDO) that powers the Control andInformation section and a battery management system (BMS) that provideshigh level of protection and charging to the internal LiPo battery.

The components in this section have been selected carefully andthoroughly to be able to provide such an integrated and compact devicewhile providing high power to the sonication section and ensuring asteady powering of the control and information section.

Indeed, when providing high power to the aerosolisation section from a3.7V LiPo battery, the supply voltage varies a lot during operation.Without a low dropout regulator, the Control and Information sectioncould not be powered with a mandatory steady supply when the batteryvoltage drops to as low as 0.3V above the minimum ratings of thecomponents in this section, which is why the LDO plays a crucial rolehere. A loss in the CI section would disturb or even stop thefunctioning of the entire device.

This is why the careful selection of components not only ensures highreliability of the device but also allows it to work under harshconditions and for a longer consecutive time between recharge.

Controlled Aerosolisation

The device is a precise, reliable and a safe aerosolisation solution formedical prescription and daily customer usage and, as such, must providea controlled and trusted aerosolisation.

This is performed through an internal method that can be broken apartinto several sections as follows:

1. Sonication

In order to provide the most optimal aerosolisation the ultrasonictransducer (PZT) needs to vibrate in the most efficient way.

Frequency

The electromechanical properties of piezoelectrical ceramics state thatthe component has the most efficiency at the resonant frequency. Butalso, vibrating a PZT at resonance for a long duration will inevitablyend with the failure and breaking of the component which renders theaerosol chamber unusable.

Another important point to consider when using piezoelectrical materialsis the inherent variability during manufacturing and its variabilityover temperature and lifetime.

Resonating a PZT at 3 MHz in order to create droplets of a size <1 umrequires an adaptive method in order to locate and target the ‘sweetspot’ of the particular PZT inside every aerosol chamber used with thedevice for every single inhalation.

Sweep

Because the device has to locate the ‘sweet spot’ for every singleinhalation and because of over-usage, the PZT temperature varies as thedevice uses an in-house double sweep method.

The first sweep is used when the device has not been used with aparticular aerosol chamber for a time that is considered enough for allthe thermal dissipation to occur and for the PZT to cool down to‘default temperature’. This procedure is also called a cold start.During this procedure the PZT needs a boost in order to produce therequired aerosol. This is achieved by only going over a small subset ofFrequencies between 2900 kHz to 2960 kHz which, considering extensivestudies and experiments, covers the resonant point.

For each frequency in this range, the sonic engine in activated and thecurrent going through the PZT is actively monitored and stored by themicrocontroller via an Analog-to-Digital Converter (ADC), and convertedback to current in order to be able to precisely deduct the Power usedby the PZT.

This yields the cold profile of this PZT regarding frequency and theFrequency used throughout the inhalation is the one that uses the mostcurrent, meaning the lowest impedance Frequency.

The second sweep is performed during any subsequent inhalation and coverthe entire range of frequencies between 2900 kHz to 3100 kHz due to themodification of the PZT profile with regards to temperature anddeformation. This hot profile is used to determine the shift to apply.

Shift

Because the aerosolisation must be optimal, the shift is not used duringany cold inhalation and the PZT will hence vibrate at resonantfrequency. This can only happen for a short and unrepeated duration oftime otherwise the PZT would inevitably break.

The shift however is used during most of inhalations as a way to stilltarget a low impedance frequency, thus resulting in quasi-optimaloperation of the PZT while protecting it against failures.

Because the hot and cold profiles are stored during inhalation themicrocontroller can then select the proper shifted frequency accordingto the measured values of current through the PZT during sweep andensure a safe mechanical operation.

The selection of the direction to shift is crucial as thepiezoelectrical component behaves in a different way if outside theduplet resonant/anti-resonant frequency or inside this range. Theselected shift should always be in this range defined by Resonant toanti-Resonant frequencies as the PZT is inductive and not capacitive.

Finally, the percentage to shift is maintained below 10% in order tostill remain close to the lowest impedance but far enough of theresonance.

Adjustment

Because of the intrinsic nature of PZTs, every inhalation is different.Numerous parameters other than the piezoelectrical element influence theoutcome of the inhalation, like the amount of e-liquid remaining insidethe aerosol chamber, the wicking state of the gauze or the battery levelof the device.

As of this, the device permanently monitors the current used by the PZTinside the aerosol chamber and the microcontroller constantly adjuststhe parameters such as the frequency and the Duty Cycle in order toprovide the aerosol chamber with the most stable power possible within apre-defined range that follows the studies and experimental results formost optimal safe aerosolisation.

Battery Monitoring

In order to provide an AC voltage of 15V and maintain a current insidethe PZT around 2.5 A, the current drawn from the battery reaches around7 to 8 Amps, which in turn, creates a drop in the battery voltage. Anycommon LiPo battery would not sustain this demanding resource for theduration of an inhalation that can top 6 s.

This is the reason why a custom LiPo battery is developed that canhandle around 11 Amps, which is 50% more than the maximum allowed in thePZT at all time, while still being simple to use in compact andintegrated portable device.

Because the battery voltage drops and varies a lot when activating thesonication section, the microcontroller constantly monitors the powerused by the PZT inside the aerosol chamber to ensure a proper but alsosafe aerosolisation.

And because the key to aerosolisation is control, the device ensuresfirst that the Control and Information section of the device alwaysfunction and does not stop in the detriment of the sonication section.

This is why the adjustment method also takes into great account the realtime battery level and, if need be, modifies the parameters like theDuty Cycle to maintain the battery at a safe level, and in the case of alow battery before starting the sonic engine, the Control andInformation section will prevent the activation.

Power Control

As being said, the key to aerosolisation is control and the method usedin the device is a real time multi-dimensional function that takes intoaccount the profile of the PZT, the current inside the PZT and thebattery level of the device at all time.

All this is only achievable thanks to the use of a microcontroller thatcan monitor and control every element of the device to produce anoptimal inhalation.

1. Inhalation Control

The device is a safe device and confirmed by BNS (Broughton NicotineServices) report, but in order to guarantee the safety of misting andthe integrity of both the aerosol chamber and the device, eachinhalation has to be controlled.

Inhalation Duration

In order to reduce the exposure to carbonyls and other toxic componentsthat might result from the heating of e-liquid, the maximum duration ofan inhalation is set to 6 seconds which completely ensure that theexposure to these components is contained.

Interval

Because the device relies on a piezoelectrical component, the deviceprevents the activation of the sonication section if an inhalationstops. The safety delay in between two inhalations is adaptive dependingon the duration of the previous one. This allows the gauze to wickproperly before the next activation.

With this functioning, the device can safely operate and theaerosolisation is rendered more optimal with no risk of breaking the PZTelement nor exposing the user to toxic components.

Connectivity (BLE)

The device Control and Information section is composed of a wirelesscommunication system in the form of a Bluetooth Low Energy capablemicrocontroller. The wireless communication system is in communicationwith the processor of the device and is configured to transmit andreceive data between the driver device and a computing device, such as asmartphone.

The connectivity via Bluetooth Low Energy to a companion mobileapplication ensures that only small power for this communication isrequired thus allowing the device to remain functioning for a longerperiod of time if not used at all, compared to traditional wirelessconnectivity solutions like Wi-Fi, classic Bluetooth, GSM or even LTE-Mand NB-IOT.

Most importantly, this connectivity is what enables the OTP as a featureand the complete control and safety of the inhalations. Every data fromresonant frequency of an inhalation to the one used, or the negativepressure created by the user and the duration are stored and transferredover BLE for further analysis and improvements of the embedded software.

Moreover, all these information are crucial when the device is used inmedical programs because it gives doctors and users all the informationregarding the process of inhalation and the ability to track inreal-time the prescriptions and the usage.

Finally, this connectivity enables the update of the embedded firmwareinside the device and over the air (OTA), which guarantees that thelatest versions can always be deployed rapidly. This gives greatscalability to the device and insurance that the device is intended tobe maintained.

Data Collection for Clinical Purposes

The device can collect user data such as number of puffs and puffduration in order to determine the total amount of therapeutic consumedby the user in a session.

This data can be interpreted by an algorithm that sets consumptionlimits per time period based on a physician's recommendations.

This will allow a controlled therapeutic dose of drug to be administeredto the user that is controlled by a physician or pharmacist and cannotbe abused by the end user.

The physician would be able to gradually lower dosages over time in acontrolled method that is safe for the user.

Puff Limitations

The process of ultrasonic cavitation has a significant impact on thenicotine concentration in the produced mist.

A device limitation of <7 second puff durations will limit the user toexposure of carbonyls commonly produced by electronic nicotine deliverysystems.

Based on Broughton Nicotine Services' experimental results, after a userperforms 10 consecutive puffs of <7 seconds, the total amount ofcarbonyls is <2.67 μg/10 puffs (average: 1.43 μg/10 puffs) forformaldehyde, <0.87 μg/10 puffs (average: 0.50 μg/10 puffs) foracetaldehyde, <0.40 μg/10 puffs (average: 0.28 μg/10 puffs) forpropionaldehyde, <0.16 μg/10 puffs (average: 0.16 μg/10 puffs) forcrotonaldehyde, <0.19 μg/10 puffs (average: 0.17 μg/10 puffs) forbutyraldehyde, <0.42 μg/10 puffs (average: 0.25 μg/10 puffs) fordiacetyl, and acetylpropionyl was not detected at all in the emissionsafter 10 consecutive <7 second puffs.

Because the aerosolisation of the e-liquid is achieved via themechanical action of the piezoelectric disc and not due to the directheating of the liquid, the individual components of the e-liquid(propylene glycol, vegetable glycerine, flavouring components, etc.)remain largely in-tact and are not broken into smaller, harmfulcomponents such as acrolein, acetaldehyde, formaldehyde, etc. at thehigh rate seen in traditional ENDS.

In order to limit the user's exposure to carbonyls while using theultrasonic device, puff length is limited to 6 seconds maximum so thatthe above results would be the absolute worst-case scenario in terms ofexposure.

Referring now to FIGS. 59 and 60 , when the end cap 248 is mounted tothe driver device housing 246, the driver device housing 246, beingaluminium, acts as a Faraday cage, preventing the device from emittingany electromagnetic waves. The device with the driver device housing 246has been tested for Electromagnetic Compatibility (EMC) and the testsreveal that the emissions are less than half the allowed limit fordevices. The EMC test results are shown in the graph of FIG. 61 .

A mist inhaler device of other examples of this disclosure comprisesmost of or preferably all of the elements of the mist generator device200 described above, but with the memory of the driver device 202storing instructions which, when executed by the processor, provideadditional functionality to the mist inhaler device.

In one example, the mist inhaler device 200 comprises an active powermonitor which incorporates a current sensor, such as the current sensor335 described above, for sensing an rms drive current of the AC drivesignal driving the ultrasonic transducer 215. The active power monitorprovides a monitoring signal which is indicative of the sensed drivecurrent, as described above.

The additional functionality of this example enables the mist inhalerdevice 200 to monitor the operation of the ultrasonic transducer whilethe ultrasonic transducer is activated. The mist inhaler device 200calculates an effectiveness value or quality index which is indicativeof how effective the ultrasonic transducer is operating to atomise aliquid within the device. The device uses the effectiveness value tocalculate the actual amount of mist that was generated over the durationof activation of the ultrasonic transducer.

Once the actual amount of mist has been calculated, the device isconfigured to calculate the actual amount of a therapeutic which waspresent in the mist and hence the actual amount of a therapeutic whichwas inhaled by a user based on the concentration of the therapeutic inthe liquid. Knowing the exact amount of a therapeutic which is deliveredto a user is particularly important when the mist inhaler device isbeing used as part of a therapeutic treatment program. Knowing the exactamount of therapeutic which is delivered to a user during eachinhalation or puff allows for the therapeutic treatment program tooperate more accurately and effectively compared with using aconventional device which simply counts the number of inhalations orpuffs, with each inhalation or puff assumed to deliver the same quantityof therapeutic to a user.

In practice, as described above, there are many different factors whichaffect the operation of an ultrasonic transducer and which have animpact on the amount of mist which is generated by the ultrasonictransducer and hence the actual amount of a therapeutic which isdelivered to a user.

For instance, if an ultrasonic transducer within a mist inhaler deviceis not operating in an optimal manner due to a low charge in the batteryreducing the current flowing through the ultrasonic transducer, a loweramount of mist will be generated and a lower amount of a therapeuticwill be delivered to a user compared with if the device was operatingoptimally. The device may thus allow a greater number of puffs for auser in order to deliver a set amount of therapeutic to the user over aperiod of time compared with the number of puffs that would be permittedif the ultrasonic transducer was operating optimally. This enables thetherapeutic treatment program to operate more effectively and preciselycompared with a conventional program which relies on using a devicewhich simply counts and restricts the number of puffs taken by a user.

The configuration of the mist inhaler device and a method of generatingmist using the mist inhaler device of some examples will now bedescribed in detail below.

In this example, the mist inhaler device incorporates the components ofthe mist inhaler device 200 described above, but the memory of thedriver device 202 further stores instructions which, when executed bythe processor, cause the processor to activate the mist generator device200 for a first predetermined length of time. As described above, themist generator device is activated by driving the ultrasonic transducer215 in the mist generator device 200 with the AC drive signal so thatthe ultrasonic transducer 215 atomises liquid carried by the capillaryelement 222.

The executed instructions cause the processor to sense, using a currentsensor, periodically during the first predetermined length of time thecurrent of the AC drive signal flowing through the ultrasonic transducer215 and storing periodically measured current values in the memory.

The executed instructions cause the processor to calculate aneffectiveness value using the current values stored in the memory. Theeffectiveness value is indicative of the effectiveness of the operationof the ultrasonic transducer at atomising the liquid.

In one example, the executed instructions cause the processor tocalculate the effectiveness value using this equation:

$Q_{I} = \frac{\sum_{t = 0}^{t = D}\frac{\sqrt{Q_{A(t)}^{2} + Q_{F(t)}^{2}}}{\sqrt{2}}}{N}$

where:

-   -   Q_(I) is the effectiveness value,    -   Q_(F) is a frequency sub-effectiveness value which is based on        the monitored frequency value (the frequency at which the        ultrasonic transducer 215 is being driven),    -   Q_(A) is an analogue to digital converter sub-effectiveness        value which is based on the measured current value (the rms        current flowing through the ultrasonic transducer 215),    -   t=0 is the start of the first predetermined length of time,    -   t=D is the end of the first predetermined length of time,    -   N is the number of periodic measurements (samples) during the        first predetermined length of time, and    -   √{square root over (2)} is a normalization factor.

In one example, the memory stores instructions which, when executed bythe processor, cause the processor to measure periodically during thefirst predetermined length of time the duty cycle of the AC drive signaldriving the ultrasonic transducer and storing periodically measured dutycycle values in the memory. The mist inhaler device then modifies theanalogue to digital converter sub-effectiveness value Q_(A) based on thecurrent values stored in the memory. Consequently, the mist inhalerdevice of this example takes into account variations in the duty cyclewhich may occur throughout the activation of the ultrasonic transducer215 when the device calculates the effectiveness value. The mist inhalerdevice can therefore calculate the actual amount of mist which isgenerated accurately by taking into account variations in the duty cycleof the AC drive signal which may occur while the ultrasonic transduceris activated.

In one example, the memory stores instructions which, when executed bythe processor, cause the processor to measure periodically during thefirst predetermined length of time a voltage of a battery which ispowering the mist generator device and storing periodically measuredbattery voltage values in the memory. The mist inhaler device thenmodifies the analogue to digital converter sub-effectiveness value Q_(A)based on the battery voltage values stored in the memory. Consequently,the mist inhaler device of this example takes into account variations inthe battery voltage which may occur throughout the activation of theultrasonic transducer 215 when the device calculates the effectivenessvalue. The mist inhaler device can therefore calculate the actual amountof mist which is generated accurately by taking into account variationsin the battery voltage which may occur while the ultrasonic transduceris activated.

The effectiveness value is used by the mist inhaler device as aweighting to calculate the actual amount of mist generated by the mistinhaler device by proportionally reducing a value of a maximum amount ofmist that would be generated if the device was operating optimally.

In one example, the memory stores instructions which, when executed bythe processor, cause the processor to measure periodically during thefirst predetermined length of time the frequency of the AC drive signaldriving the ultrasonic transducer 215 and storing periodically measuredfrequency values in the memory. The device then calculates theeffectiveness value using the using the frequency values stored in thememory, in addition to the current values as described above.

In one example, the memory stores instructions which, when executed bythe processor, cause the processor to calculate a maximum mist amountvalue that would be generated if the ultrasonic transducer 215 wasoperating optimally over the duration of the first predetermined lengthof time. In one example, the maximum mist amount value is calculatebased on modelling which determines the maximum amount of mist whichwould be generated when the ultrasonic transducer was operatingoptimally.

Once the maximum mist amount value has been calculated, the mist inhalerdevice can calculate an actual mist amount value by reducing the maximummist amount value proportionally based on the effectiveness value todetermine the actual mist amount that was generated over the duration ofthe first predetermined length of time.

Once the actual mist amount has been calculated, the mist inhaler devicecan calculate a therapeutic amount value which is indicative of theamount of a therapeutic in the actual mist amount that was generatedover the duration of the first predetermined length of time. The mistinhaler device then stores a record of the therapeutic amount value inthe memory. In this way, the mist inhaler device can record accuratelythe actual amount of a therapeutic which has been delivered to a user ineach inhalation or puff.

In one example, the memory stores instructions which, when executed bythe processor, cause the processor to selecting a second predeterminedlength of time in response to the effectiveness value. In this case, thesecond predetermined length of time is a length of time over which theultrasonic transducer 215 is activated during a second inhalation orpuff by a user. In one example, the second predetermined length of timeis equal to the first predetermined length of time but with the timereduced or increased proportionally according to the effectivenessvalue. For instance, if the effectiveness value indicates that theultrasonic transducer 215 is not operating effectively, the secondpredetermined length of time is made longer by the effectiveness valuesuch that a desired amount of mist is generated during the secondpredetermined length of time.

When it comes to the next inhalation, the mist inhaler device activatesthe mist generator device for the second predetermined length of time sothat the mist generator device generates a predetermined amount of mistduring the second predetermined length of time. The mist inhaler devicethus controls the amount of mist generated during the secondpredetermined length of time accurately, taking into account the variousparameters which are reflected by the effectiveness value which affectthe operation of the mist inhaler device.

In one example, the memory stores instructions which, when executed bythe processor, cause the processor to activate the mist generator devicefor a plurality of predetermined lengths of time. For instance, the mistgenerator device is activated during a plurality of successiveinhalations or puffs by a user.

The mist inhaler device stores a plurality of therapeutic amount valuesin the memory, each therapeutic amount value being indicative of theamount of a therapeutic in the mist that was generated over the durationof a respective one of the predetermined lengths of time. In oneexample, the mist inhaler device prevents further activation of the mistgenerator device for a predetermined duration if the total amount of thetherapeutic in the mist that was generated over the duration of thepredetermined lengths of time is equal to or greater than apredetermined threshold. In one example, the predetermined duration is aduration in the range of 1 to 24 hours. In other examples, thepredetermined duration is 24 hours or 12 hours.

The mist inhaler of some examples of this disclosure is configured totransmit data indicative of the therapeutic amount values from the mistgenerator device to a computing device (e.g. via Bluetooth™ Low Energycommunication) for storage in a memory of the computing device (e.g. asmartphone). An executable application running on the computing devicecan thus log the amount of a therapeutic which has been delivered to auser. The executable application can also control the operation of themist inhaler device to limit the activation of the mist inhaler deviceto restrict the amount of a therapeutic being delivered to a user over aperiod of time.

The mist inhaler device of some examples of this disclosure is thereforeconfigured to prevent further activation once a user has consumed a setamount of a therapeutic during a set timeframe, such as the amount oftherapeutic consumed during a day.

All of the above applications involving ultrasonic technology canbenefit from the optimisation achieved by the frequency controller whichoptimises the frequency of sonication for optimal performance.

It is to be appreciated that the disclosures herein are not limited touse for nicotine delivery. Indeed, in some examples, the mist inhalerdevice contains a liquid comprising a therapeutic which does notcomprise nicotine. Some examples are configured for use for variousmedical purposes (e.g. the delivery of CBD for pain relief, supplementsfor performance enhancement, albuterol/salbutamol for asthma patients,etc.)

The devices disclosed herein are for use with any therapeutics, drugs orother compounds, with the drug or compound being provided in a liquidwithin the liquid chamber of the device for aerosolisation by thedevice. In some examples, the devices disclosed herein are for use withtherapeutics, drugs and compounds including, but not limited to, thefollowing:

-   -   Respiratory    -   Bronchodilators    -   Olodaterol    -   Levalbuterol    -   Berodual (Ipratropium bromide/Fenoterol)    -   Combivent (Ipratropium bromide/Salbutamol)    -   Anti-inflammatory    -   Betamethasone    -   Dexamethasone    -   Methylprednisolone    -   Hydrocortisone    -   Mucolytics    -   N-Acetylcysteine    -   Pulmonary Hypertension    -   Sildenafil    -   Tadalafil    -   Epoprostenol    -   Treprostenil    -   Iloprost    -   Infectious Disease    -   Antimicrobials    -   Aminoglycosides (Gentamicin, Tobramycin, Amikacin, Colomycin,        Neomycin, Liposomal Amikacin)    -   Quinolones (Ciprofloxacin, Levofloxacin, Moxifloxacin Ofloxacin)    -   Macrolides (Azithromycin)    -   Minocycline    -   Betalactams (Piperacillin-Tazobactam, Ceftazidime Ticarcillin)    -   Cephalosporins (Cefotaxime, Cefepime, Ceftriaxone, Cefotaxime)    -   Glycopeptides (Vancomycin)    -   Meropenem    -   Polymixin (Colistin, Polymixin B)    -   Antifunqals    -   Amphotericin    -   Fluconazole    -   Caspofungen    -   Antivirals    -   Valganciclovir    -   Favipiravir    -   Remdisivir    -   Acyclovir    -   Anti TB    -   Isoniazid    -   Pyrazinamide    -   Rifampin    -   Ethambutol    -   Oncology    -   Biologics    -   Gilotrif    -   Afatinib    -   Caplacizumab    -   Dupilumab    -   Isarilumab    -   Alirucomab    -   Volasertib    -   Nintedanib    -   Imatinib    -   Sirolimus    -   Chemotherapy    -   Azacitidine    -   Decitabine    -   Docetaxel    -   Gemcitabine    -   Cisplatinum    -   CNS & PSYCH    -   Sodium valproate    -   Teriflunomide    -   Zomitriptan    -   METABOLIC/HORMONAL    -   Insulin    -   Estrogen    -   IMMUNOLOGY    -   Vaccine    -   Monoclonal Antibodies    -   Stem Cells    -   Vitamins    -   Zinc    -   Ascorbic Acid    -   Miscellaneous    -   Niclosamide    -   Hydroxychloroquine    -   Ivermectin

The ultrasonic mist inhaler 100 of some examples is a more powerfulversion of current portable medical nebulizers.

Other examples of the ultrasonic mist inhaler devices are easilyenvisioned, including medicinal delivery devices which do not have theappearance of a cigarette.

The foregoing outlines features of several examples or embodiments sothat those of ordinary skill in the art may better understand variousaspects of the present disclosure. Those of ordinary skill in the artshould appreciate that they may readily use the present disclosure as abasis for designing or modifying other processes and structures forcarrying out the same purposes and/or achieving the same advantages ofvarious examples or embodiments introduced herein. Those of ordinaryskill in the art should also realise that such equivalent constructionsdo not depart from the spirit and scope of the present disclosure, andthat they may make various changes, substitutions, and alterationsherein without departing from the spirit and scope of the presentdisclosure.

Although the subject matter has been described in language specific tostructural features or methodological acts, it is to be understood thatthe subject matter of the appended claims is not necessarily limited tothe specific features or acts described above. Rather, the specificfeatures and acts described above are disclosed as example forms ofimplementing at least some of the claims.

Various operations of examples or embodiments are provided herein. Theorder in which some or all of the operations are described should not beconstrued to imply that these operations are necessarily orderdependent. Alternative ordering will be appreciated having the benefitof this description. Further, it will be understood that not alloperations are necessarily present in each embodiment provided herein.Also, it will be understood that not all operations are necessary insome examples or embodiments.

Moreover, “exemplary” is used herein to mean serving as an example,instance, illustration, etc., and not necessarily as advantageous. Asused in this application, “or” is intended to mean an inclusive “or”rather than an exclusive “or”. In addition, “a” and “an” as used in thisapplication and the appended claims are generally be construed to mean“one or more” unless specified otherwise or clear from context to bedirected to a singular form. Also, at least one of A and B and/or thelike generally means A or B or both A and B. Furthermore, to the extentthat “includes”, “having”, “has”, “with”, or variants thereof are used,such terms are intended to be inclusive in a manner similar to the term“comprising”. Also, unless specified otherwise, “first,” “second,” orthe like are not intended to imply a temporal aspect, a spatial aspect,an ordering, etc. Rather, such terms are merely used as identifiers,names, etc. for features, elements, items, etc. For example, a firstelement and a second element generally correspond to element A andelement B or two different or two identical elements or the sameelement.

Also, although the disclosure has been shown and described with respectto one or more implementations, equivalent alterations and modificationswill occur to others of ordinary skill in the art based upon a readingand understanding of this specification and the annexed drawings. Thedisclosure comprises all such modifications and alterations and islimited only by the scope of the following claims. In particular regardto the various functions performed by the above described features(e.g., elements, resources, etc.), the terms used to describe suchfeatures are intended to correspond, unless otherwise indicated, to anyfeatures which performs the specified function of the described features(e.g., that is functionally equivalent), even though not structurallyequivalent to the disclosed structure. In addition, while a particularfeature of the disclosure may have been disclosed with respect to onlyone of several implementations, such feature may be combined with one ormore other features of the other implementations as may be desired andadvantageous for any given or particular application.

Examples or embodiments of the subject matter and the functionaloperations described herein can be implemented in digital electroniccircuitry, or in computer software, firmware, or hardware, including thestructures disclosed in this specification and their structuralequivalents, or in combinations of one or more of them.

Some examples or embodiments are implemented using one or more modulesof computer program instructions encoded on a computer-readable mediumfor execution by, or to control the operation of, a data processingapparatus. The computer-readable medium can be a manufactured product,such as hard drive in a computer system or an embedded system. Thecomputer-readable medium can be acquired separately and later encodedwith the one or more modules of computer program instructions, such asby delivery of the one or more modules of computer program instructionsover a wired or wireless network. The computer-readable medium can be amachine-readable storage device, a machine-readable storage substrate, amemory device, or a combination of one or more of them.

The terms “computing device” and “data processing apparatus” encompassall apparatus, devices, and machines for processing data, including byway of example a programmable processor, a computer, or multipleprocessors or computers. The apparatus can include, in addition tohardware, code that creates an execution environment for the computerprogram in question, e.g., code that constitutes processor firmware, aprotocol stack, a database management system, an operating system, aruntime environment, or a combination of one or more of them. Inaddition, the apparatus can employ various different computing modelinfrastructures, such as web services, distributed computing and gridcomputing infrastructures.

The processes and logic flows described in this specification can beperformed by one or more programmable processors executing one or morecomputer programs to perform functions by operating on input data andgenerating output.

Processors suitable for the execution of a computer program include, byway of example, both general and special purpose microprocessors, andany one or more processors of any kind of digital computer. Generally, aprocessor will receive instructions and data from a read-only memory ora random access memory or both. The essential elements of a computer area processor for performing instructions and one or more memory devicesfor storing instructions and data. Generally, a computer will alsoinclude, or be operatively coupled to receive data from or transfer datato, or both, one or more mass storage devices for storing data, e.g.,magnetic, magneto-optical disks, or optical disks. However, a computerneed not have such devices. Devices suitable for storing computerprogram instructions and data include all forms of non-volatile memory,media and memory devices.

In the present specification “comprise” means “includes or consists of”and “comprising” means “including or consisting of”.

The features disclosed in the foregoing description, or the followingclaims, or the accompanying drawings, expressed in their specific formsor in terms of a means for performing the disclosed function, or amethod or process for attaining the disclosed result, as appropriate,may, separately, or in any combination of such features, be utilised forrealising the invention in diverse forms thereof.

Representative Features

Representative features are set out in the following clauses, whichstand alone or may be combined, in any combination, with one or morefeatures disclosed in the text and/or drawings of the specification.

1. A mist inhaler device for generating a mist containing a therapeuticfor inhalation by a user, the device comprising:

-   -   a mist generator device which incorporates:        -   a mist generator housing which is elongate and comprises an            air inlet port and a mist outlet port;        -   a liquid chamber provided within the mist generator housing,            the liquid chamber containing a liquid to be atomised, the            liquid comprising a therapeutic;        -   a sonication chamber provided within the mist generator            housing;        -   a capillary element extending between the liquid chamber and            the sonication chamber such that a first portion of the            capillary element is within the liquid chamber and a second            portion of the capillary element is within the sonication            chamber;        -   an ultrasonic transducer having an atomisation surface,            wherein part of the second portion of the capillary element            is superimposed on part of the atomisation surface, and            wherein when the ultrasonic transducer is driven by an AC            drive signal the atomisation surface vibrates to atomise the            liquid carried by the second portion of the capillary            element to generate a mist comprising the atomised liquid            and air within the sonication chamber; and        -   an airflow arrangement which provides an air flow path            between the air inlet port, the sonication chamber and the            air outlet port such that a user drawing on the mist outlet            port draws air through the inlet port, through the            sonication chamber and out through the mist outlet port,            with the mist generated in the sonication chamber being            carried by the air out through the mist outlet port for            inhalation by the user, wherein the device further            comprises:    -   a driver device which incorporates:        -   a battery;        -   an H-bridge circuit which is connected to the ultrasonic            transducer, wherein the H-bridge circuit generates an AC            drive signal to drive the ultrasonic transducer;    -   a microchip connected to the H-bridge circuit to control the        H-bridge circuit to generate the AC drive signal, wherein the        microchip is a single unit which comprises a plurality of        interconnected embedded components and subsystems comprising:    -   an oscillator which generates:        -   a main clock signal,        -   a first phase clock signal which is high for a first time            during the positive half-period of the main clock signal and            low during the negative half-period of the main clock            signal, and        -   a second phase clock signal which is high for a second time            during the negative half-period of the main clock signal and            low during the positive half-period of the main clock            signal, wherein the phases of the first phase clock signal            and the second phase clock signal are centre aligned;    -   a pulse width modulation (PWM) signal generator subsystem        comprising:        -   a delay locked loop which generates a double frequency clock            signal using the first phase clock signal and the second            phase clock signal, the double frequency clock signal being            double the frequency of the main clock signal, wherein the            delay locked loop controls the rising edge of the first            phase clock signal and the second phase clock signal to be            synchronous with the rising edge of the double frequency            clock signal, and wherein the delay locked loop adjusts the            frequency and the duty cycle of the first phase clock signal            and the second phase clock signal in response to a driver            control signal to produce a first phase output signal and a            second phase output signal, wherein the first phase output            signal and the second phase output signal are configured to            drive the H-bridge circuit to generate an AC drive signal to            drive the ultrasonic transducer;        -   a first phase output signal terminal which outputs the first            phase output signal to the H-bridge circuit;        -   a second phase output signal terminal which outputs the            second phase output signal to the H-bridge circuit;        -   a feedback input terminal which receives a feedback signal            from the H-bridge circuit, the feedback signal being            indicative of a parameter of the operation of the H-bridge            circuit or AC drive signal when the H-bridge circuit is            driving the ultrasonic transducer with the AC drive signal            to atomise the liquid;    -   an analogue to digital converter (ADC) subsystem comprising:        -   a plurality of ADC input terminals which receive a plurality            of respective analogue signals, wherein one ADC input            terminal of the plurality of ADC input terminals is            connected to the feedback input terminal such that the ADC            subsystem receives the feedback signal from the H-bridge            circuit, and wherein the ADC subsystem samples analogue            signals received at the plurality of ADC input terminals at            a sampling frequency which is proportional to the frequency            of the main clock signal and the ADC subsystem generates ADC            digital signals using the sampled analogue signals;    -   a digital processor subsystem which receives the ADC digital        signals from the ADC subsystem and processes the ADC digital        signals to generate the driver control signal, wherein the        digital processor subsystem communicates the driver control        signal to the PWM signal generator subsystem to control the PWM        signal generator subsystem; and    -   a digital to analogue converter (DAC) subsystem comprising:        -   a digital to analogue converter (DAC) which converts a            digital control signal generated by the digital processor            subsystem into an analogue voltage control signal to control            a voltage regulator circuit which generates a voltage for            modulation by the H-bridge circuit; and        -   a DAC output terminal which outputs the analogue voltage            control signal to control the voltage regulator circuit to            generate a predetermined voltage for modulation by the            H-bridge circuit to drive the ultrasonic transducer in            response to feedback signals which are indicative of the            operation of the ultrasonic transducer.

2. The device of clause 1, wherein the microchip further comprises:

-   -   a frequency divider which is connected to the oscillator to        receive the main clock signal from the oscillator, the frequency        divider dividing the main clock signal by a predetermined        divisor amount and outputting the frequency reference signal to        the delay locked loop.

3. The device of clause 1, wherein the delay locked loop comprises aplurality of delay lines connected end to end, wherein the total delayof the delay lines is equal to the period of the main clock signal.

4. The device of clause 3, wherein the delay locked loop adjusts theduty cycle of the first phase clock signal and the second phase clocksignal in response to the driver control signal by varying the delay ofeach delay line in the delay locked loop.

5. The device of clause 1, wherein the feedback input terminal receivesa feedback signal from the H-bridge circuit in the form of a voltagewhich indicative of an rms current of an AC drive signal which isdriving the resonant circuit.

6. The device of clause 1, wherein the ADC subsystem comprises aplurality of further ADC input terminals which receive feedback signalswhich are indicative of at least one of the voltage of the battery orthe voltage of a battery charger connected to the device.

7. The device of clause 1, wherein the microchip further comprises:

-   -   a temperature sensor which is embedded within the microchip,        wherein the temperature sensor generates a temperature signal        which is indicative of the temperature of the microchip, and        wherein the temperature signal is received by a further ADC        input terminal of the ADC subsystem and the temperature signal        is sampled by the ADC.

8. The device of clause 1, wherein the ADC subsystem samples signalsreceived at the plurality of ADC input terminals sequentially with eachsignal being sampled by the ADC subsystem a respective predeterminednumber of times.

9. The device of clause 1, wherein the microchip further comprises:

-   -   a battery charging subsystem which controls the charging of the        battery.

10. The device of clause 1, wherein the DAC subsystem comprises:

-   -   a further digital to analogue converter (DAC) which converts a        further digital control signal generated by the digital        processor subsystem into a further analogue voltage control        signal to control the voltage regulator circuit.

11. The device of clause 1, wherein the device further comprises:

-   -   a further microchip, wherein the further microchip is a single        unit which comprises a plurality of interconnected embedded        components and subsystems comprising:        -   a first power supply terminal;        -   a second power supply terminal;        -   the H-bridge circuit which incorporates a first switch, a            second switch, a third switch and a fourth switch, wherein:        -   the first switch and the third switch are connected in            series between the first power supply terminal and the            second power supply terminal;        -   a first output terminal is connected electrically between            the first switch and the third switch, wherein the first            output terminal is connected to a first terminal of the            ultrasonic transducer,        -   the second switch and the fourth switch are connected in            series between the first power supply terminal and the            second power supply terminal, and        -   a second output terminal is connected electrically between            the second switch and the fourth switch, wherein the second            output terminal is connected to a second terminal of the            ultrasonic transducer;        -   a first phase terminal which receives the first phase output            signal from the pulse width modulation (PWM) signal            generator subsystem;        -   a second phase terminal which receives a second phase output            signal from the PWM signal generator subsystem;        -   a digital state machine which generates timing signals based            on the first phase output signal and the second phase output            signal and outputs the timing signals to the switches of the            H-bridge circuit to control the switches to turn on and off            in a sequence such that the H-bridge circuit outputs an AC            drive signal for driving the ultrasonic transducer, wherein            the sequence comprises a free-float period in which the            first switch and the second switch are turned off and the            third switch and the fourth switch are turned on in order to            dissipate energy stored by the ultrasonic transducer;        -   a current sensor which incorporates:            -   a first current sense resistor which is connected in                series between the first switch and the first power                supply terminal;            -   a first voltage sensor which measures the voltage drop                across the first current sense resistor and provides a                first voltage output which is indicative of the current                flowing through the first current sense resistor;            -   a second current sense resistor which is connected in                series between the second switch and the first power                supply terminal;            -   a second voltage sensor which measures the voltage drop                across the second current sensor resistor and provides a                second voltage output which is indicative of the current                flowing through the second current sense resistor; and            -   a current sensor output terminal which provides an rms                output voltage relative to ground which is equivalent to                the first voltage output and the second voltage output,        -   wherein the rms output voltage is indicative of an rms            current flowing through the first switch or the second            switch and the current flowing through the ultrasonic            transducer which is connected between the first output            terminal and the second output terminal.

12. The device of clause 11, wherein the H-bridge circuit is configuredto output a power of 22 W to 50 W to the ultrasonic transducer which isconnected to the first output terminal and the second output terminal.

13. The device of clause 11, wherein the further microchip comprises:

-   -   a temperature sensor which is embedded within the further        microchip, wherein the temperatures sensor measures the        temperature of the further microchip and disables at least part        of the further microchip in the event that the temperature        sensor senses that the further microchip is at a temperature        which is in excess of a predetermined threshold.

14. The device of clause 11, wherein the device further comprises:

-   -   a boost converter circuit which is configured to increase the        voltage of the battery to a boost voltage in response to the        analogue voltage output signal from the DAC output terminal,        wherein the boost converter circuit provides the boost voltage        at the first power supply terminal such that the boost voltage        is modulated by the switching of the switches of the H-bridge        circuit.

15. The device of clause 11, wherein the current sensor senses thecurrent flowing through the resonant circuit during the free-floatperiod and the digital state machine adapts the timing signals to switchon either the first switch or the second switch when the current sensorsenses that the current flowing through the resonant circuit during thefree-float period is zero.

16. The device of clause 11, wherein, during a setup phase of operationof the device, the further microchip:

-   -   measures the length of time taken for the current flowing        through the resonant circuit to fall to zero when the first        switch and the second switch are turned off and the third switch        and the fourth switch are turned on; and    -   sets the length of time of the free-float period to be equal to        the measured length of time.

17. The device of clause 1, wherein the device further comprises:

-   -   a processor for controlling the driver device; and    -   a memory storing instructions which, when executed by the        processor, cause the driver device to:        -   A. control the driver device to output an AC drive signal to            the ultrasonic transducer at a sweep frequency;        -   B. calculate the active power being used by the ultrasonic            transducer based on the feedback signal;        -   C. control the driver device to modulate the AC drive signal            to maximise the active power being used by the ultrasonic            transducer;        -   D. store a record in the memory of the maximum active power            used by the ultrasonic transducer and the sweep frequency of            the AC drive signal;        -   E. repeat steps A-D for a predetermined number of iterations            with the sweep frequency incrementing or decrementing with            each iteration such that, after the predetermined number of            iterations has occurred, the sweep frequency has been            incremented or decremented from a start sweep frequency to            an end sweep frequency;        -   F. identify from the records stored in the memory the            optimum frequency for the AC drive signal which is the sweep            frequency of the AC drive signal at which a maximum active            power is used by the ultrasonic transducer; and        -   G. control the driver device to output an AC drive signal to            the ultrasonic transducer at the optimum frequency to drive            the ultrasonic transducer to atomise a liquid.

18. The device of clause 17, wherein the start sweep frequency is 2900kHz and the end sweep frequency is 3100 kHz.

19. The device of clause 1, wherein the driver device is releasablyattached to the mist generator device such that the driver device isseparable from the mist generator device.

20. A mist inhaler device for generating a mist for inhalation by auser, the device comprising:

-   -   a mist generator device comprising:        -   a sonication chamber;        -   a liquid chamber containing a liquid to be atomised;        -   a capillary element extending between the liquid chamber and            the sonication chamber;        -   an ultrasonic transducer which is configured to vibrate to            atomise liquid carried by the capillary element from the            liquid chamber to the sonication chamber to generate a mist            comprising the atomised liquid and air within the sonication            chamber; and        -   a mist outlet port which is in fluid communication with the            sonication chamber such that a user drawing on the mist            outlet port inhales mist from the sonication chamber,            wherein the mist inhaler device further comprises:    -   a driver device which incorporates:        -   a battery;        -   an AC driver for converting a voltage from the battery into            an AC drive signal to drive the ultrasonic transducer to            vibrate;        -   an active power monitor for monitoring the active power used            by the ultrasonic transducer when the ultrasonic transducer            is driven by the AC drive signal, wherein the active power            monitor comprises a current sensor for sensing a drive            current of the AC drive signal driving the ultrasonic            transducer, and wherein the active power monitor arrangement            provides a monitoring signal which is indicative of the            sensed drive current;        -   a processor for controlling the AC driver and for receiving            the monitoring signal from the active power monitor; and        -   a memory storing instructions which, when executed by the            processor, cause the processor to:            -   activate the mist generator device for a first                predetermined length of time, wherein activating the                mist generator device comprises driving the ultrasonic                transducer in the mist generator device with the AC                drive signal so that the ultrasonic transducer atomises                the liquid carried by the capillary element;            -   sense, using the current sensor, periodically during the                first predetermined length of time the current of the AC                drive signal flowing through the ultrasonic transducer                and store periodically measured current values in the                memory;            -   calculate an effectiveness value using the current                values stored in the memory, the effectiveness value                being indicative of the effectiveness of the operation                of the ultrasonic transducer at atomising the liquid;            -   selecting a second predetermined length of time in                response to the effectiveness value; and            -   activate the mist generator device for the second                predetermined length of time so that the mist generator                device generates a predetermined amount of mist during                the second predetermined length of time.

21. The device of clause 20, wherein the memory stores instructionswhich, when executed by the processor, cause the processor to:

-   -   measure periodically during the first predetermined length of        time the frequency of the AC drive signal driving the ultrasonic        transducer and store periodically measured frequency values in        the memory; and    -   calculate the effectiveness value using the using the frequency        values stored in the memory.

22. The device of clause 21, wherein the memory stores instructionswhich, when executed by the processor, cause the processor to calculatethe effectiveness value using this equation:

$Q_{I} = \frac{\sum_{t = 0}^{t = D}\frac{\sqrt{Q_{A(t)}^{2} + Q_{F(t)}^{2}}}{\sqrt{2}}}{N}$

where:

-   -   Q_(I) is the effectiveness value,    -   Q_(F) is a frequency sub-effectiveness value which is based on        the monitored frequency value,    -   Q_(A) is an analog to digital converter sub-effectiveness value        which is based on the measured current value,    -   t=0 is the start of the first predetermined length of time,    -   t=D is the end of the first predetermined length of time,    -   N is the number of periodic measurements during the first        predetermined length of time, and    -   √{square root over (2)} is a normalization factor.

23. The device of clause 22, wherein the memory stores instructionswhich, when executed by the processor, cause the processor to:

-   -   measure periodically during the first predetermined length of        time the duty cycle of the AC drive signal driving the        ultrasonic transducer and storing periodically measured duty        cycle values in the memory; and    -   modify the analogue to digital converter sub-effectiveness value        Q_(A) based on the current values stored in the memory.

24. The device of clause 22 or clause 23, wherein the memory storesinstructions which, when executed by the processor, cause the processorto:

-   -   measure periodically during the first predetermined length of        time a voltage of a battery which is powering the mist generator        device and storing periodically measured battery voltage values        in the memory; and    -   modify the analogue to digital converter sub-effectiveness value        Q_(A) based on the battery voltage values stored in the memory.

25. The device of any one of the preceding clauses, wherein the memorystores instructions which, when executed by the processor, cause theprocessor to:

-   -   calculate a maximum mist amount value that would be generated if        the ultrasonic transducer was operating optimally over the        duration of the first predetermined length of time; and    -   calculate an actual mist amount value by reducing the maximum        mist amount value proportionally based on the effectiveness        value to determine the actual mist amount that was generated        over the duration of the first predetermined length of time.

26. The device of clause 25, wherein the memory stores instructionswhich, when executed by the processor, cause the processor to:

-   -   calculate a therapeutic amount value which is indicative of the        amount of therapeutic in the actual mist amount that was        generated over the duration of the first predetermined length of        time; and    -   store the therapeutic amount value in the memory.

27. The device of clause 26, wherein the memory stores instructionswhich, when executed by the processor, cause the processor to:

-   -   activate the mist generator device for a plurality of        predetermined lengths of time;    -   store a plurality of therapeutic amount values in the memory,        each therapeutic amount value being indicative of the amount of        therapeutic in the mist that was generated over the duration of        a respective one of the predetermined lengths of time; and    -   prevent further activation of the mist generator device for a        predetermined duration if the total amount of the therapeutic in        the mist that was generated over the duration of the        predetermined lengths of time is equal to or greater than a        predetermined threshold.

28. The device of clause 27, wherein the predetermined duration is aduration in the range of 1 to 24 hours.

29. The device of clause 27 or clause 28, wherein the memory storesinstructions which, when executed by the processor, cause the processorto:

-   -   transmit data indicative of the therapeutic amount values from        the mist generator device to a computing device for storage in a        memory of the computing device.

30. A method of generating mist for inhalation by a user, the methodcomprising:

-   -   activating a mist generator device for a first predetermined        length of time, wherein activating the mist generator device        comprises driving an ultrasonic transducer in the mist generator        device with an AC drive signal so that the ultrasonic transducer        vibrates to atomise a liquid to generate a mist comprising the        atomised liquid and air;    -   measuring periodically during the first predetermined length of        time the current of the AC drive signal flowing through the        ultrasonic transducer and storing periodically measured current        values in a memory;    -   calculating an effectiveness value using the current values        stored in the memory, the effectiveness value being indicative        of the effectiveness of the operation of the ultrasonic        transducer at atomising the liquid;    -   selecting a second predetermined length of time in response to        the effectiveness value; and    -   activating the mist generator device for the second        predetermined length of time so that the mist generator device        generates the predetermined amount of mist during the second        predetermined length of time.

31. The method of clause 30, wherein the method further comprises:

-   -   measuring periodically during the first predetermined length of        time the frequency of the AC drive signal driving the ultrasonic        transducer and storing periodically measured frequency values in        the memory; and    -   calculating the effectiveness value using the using the        frequency values stored in the memory.

32. The method of clause 31, wherein the method comprises calculatingthe effectiveness value using this equation:

$Q_{I} = \frac{\sum_{t = 0}^{t = D}\frac{\sqrt{Q_{A(t)}^{2} + Q_{F(t)}^{2}}}{\sqrt{2}}}{N}$

where:

-   -   Q_(I) is the effectiveness value,    -   Q_(F) is a frequency sub-effectiveness value which is based on        the monitored frequency value,    -   Q_(A) is an analog to digital converter (“ADC”)        sub-effectiveness value which is based on the measured current        value,    -   t=0 is the start of the first predetermined length of time,    -   t=D is the end of the first predetermined length of time,    -   N is the number of periodic measurements during the first        predetermined length of time, and    -   √{square root over (2)} is a normalization factor.

33. The method of clause 32, wherein the method further comprises:

-   -   measuring periodically during the first predetermined length of        time the duty cycle of the AC drive signal driving the        ultrasonic transducer and storing periodically measured duty        cycle values in the memory; and    -   modifying the analogue to digital converter (“ADC”)        sub-effectiveness value Q_(A) based on the current values stored        in the memory.

34. The method of clause 32 or clause 33, wherein the method furthercomprises:

-   -   measuring periodically during the first predetermined length of        time a voltage of a battery which is powering the mist generator        device and storing periodically measured battery voltage values        in the memory; and    -   modifying the analogue to digital converter (“ADC”)        sub-effectiveness value Q_(A) based on the battery voltage        values stored in the memory.

35. The method of any one of clauses 30 to 34, wherein the methodfurther comprises:

-   -   calculating a maximum mist amount value that would be generated        if the ultrasonic transducer was operating optimally over the        duration of the first predetermined length of time; and    -   calculating an actual mist amount value by reducing the maximum        mist amount value proportionally based on the effectiveness        value to determine the actual mist amount that was generated        over the duration of the first predetermined length of time.

36. The method of clause 35, wherein the method further comprises:

-   -   calculating a therapeutic amount value which is indicative of        the amount of therapeutic in the actual mist amount that was        generated over the duration of the first predetermined length of        time; and    -   storing the therapeutic amount value in the memory.

37. The method of clause 36, wherein the method further comprises:

-   -   activating the mist generator device for a plurality of        predetermined lengths of time;    -   storing a plurality of therapeutic amount values in the memory,        each therapeutic amount value being indicative of the amount of        therapeutic in the mist that was generated over the duration of        a respective one of the predetermined lengths of time; and    -   preventing further activation of the mist generator device for a        predetermined duration if the total amount of the therapeutic in        the mist that was generated over the duration of the        predetermined lengths of time is equal to or greater than a        predetermined threshold.

38. The method of clause 37, wherein the predetermined duration is aduration in the range of 1 to 24 hours.

39. The method of clause 37 or clause 38, wherein the method furthercomprises:

-   -   transmitting data indicative of the therapeutic amount values        from the mist generator device to a computing device for storage        in a memory of the computing device.

Although certain example embodiments of the invention have beendescribed, the scope of the appended claims is not intended to belimited solely to these embodiments. The claims are to be construedliterally, purposively, and/or to encompass equivalents.

The invention claimed is:
 1. A mist generator device for use with adriver device, the mist generator device comprising: a mist generatorhousing which is elongate and terminates at a bottom end and a top endopposite the bottom end, the housing having opposite sides positionedbetween the top end and bottom end, a central longitudinal axis passingthrough the top end and the bottom end, an air inlet port formed in thebottom end, and a mist outlet port formed in the top end; a liquidchamber provided within the mist generator housing, the liquid chambercontaining a liquid to be atomized; a sonication chamber provided withinthe mist generator housing; a capillary element extending between theliquid chamber and the sonication chamber such that a first portion ofthe capillary element is within the liquid chamber and a second portionof the capillary element is within the sonication chamber; an ultrasonictransducer having a generally planar atomization surface which isprovided within the sonication chamber and a central longitudinal axisperpendicular to the atomization surface, the ultrasonic transducerbeing mounted within the mist generator housing, wherein part of thesecond portion of the capillary element is superimposed on part of theatomization surface, and wherein the ultrasonic transducer is configuredto vibrate the atomization surface to atomize the liquid carried by thesecond portion of the capillary element to generate a mist comprisingthe atomized liquid and air within the sonication chamber; and anairflow arrangement within the mist generator housing which provides anair flow path between the air inlet port, the sonication chamber and theair outlet port, the airflow arrangement comprising: a first portioninitiating at the air inlet port, the first portion of the airflowarrangement having a longitudinal axis that is substantially parallel tothe central longitudinal axis of the housing and passing through the airinlet port, the first portion continuing to a second portion of theairflow arrangement and being in direct communication with thesonication chamber, the second portion of the airflow arrangement havinga central longitudinal axis that is substantially perpendicular to thecentral longitudinal axis of the housing and is substantiallyperpendicular to the plane of the atomisation surface of the ultrasonictransducer, the central longitudinal axis of the second portionintersecting at least a portion of the atomization surface and beingconcentric with the central longitudinal axis of the ultrasonictransducer such that the direction of the flow of air into thesonication chamber is substantially perpendicular to the plane of theatomisation surface of the ultrasonic transducer, the first portion ofthe airflow arrangement extending from the bottom end to the secondportion of the airflow arrangement, wherein the airflow arrangement isconfigured to guide a direction of a flow of air along the airflow pathsuch that the flow of air is substantially perpendicular and concentricto the atomization surface of the ultrasonic transducer as the flow ofair enters into the sonication chamber.
 2. The mist generator device ofclaim 1, wherein the airflow arrangement is configured to guide thedirection of the flow of air along the airflow path such that the flowof air from the air inlet port is substantially parallel with thecentral longitudinal axis of the mist generator housing prior to passinginto the sonication chamber.
 3. The mist generator device of claim 2,wherein the second portion of the airflow arrangement is configured tochange the direction of the flow of air approximately 90° to besubstantially perpendicular and concentric to the atomization surface ofthe ultrasonic transducer as the flow of air passes into the sonicationchamber.
 4. The mist generator device of claim 1, wherein the airflowarrangement is configured to guide the direction of the flow of airalong the airflow path such that the flow of air from the sonicationchamber is substantially parallel with the central longitudinal axis ofthe mist generator housing from the sonication chamber to the air outletport.
 5. The mist generator device of claim 4, wherein the airflowarrangement is configured to change the direction of the flow of airapproximately 90° to be substantially parallel with the centrallongitudinal axis of the mist generator housing as the flow of airpasses out of the sonication chamber and toward the air outlet port. 6.The mist generator device of claim 1, wherein the airflow arrangementprovides an airflow path having an average cross-sectional area ofsubstantially 11.5 mm².
 7. The mist generator device of claim 1, whereinthe sonication chamber is unobstructed to permit the flow of airdirectly to the atomization surface of the ultrasonic transducer as theflow of air passes into the sonication chamber.
 8. The mist generatordevice of claim 1, wherein the mist generator device further comprises:a transducer holder which is held within the mist generator housing,wherein the transducer holder holds the ultrasonic transducer andretains the second portion of the capillary element superimposed on partof the atomization surface; and a divider portion which provides abarrier between the liquid chamber and the sonication chamber, whereinthe divider portion comprises a capillary aperture through which part ofthe first portion of the capillary element extends.
 9. The mistgenerator device of claim 8, wherein the transducer holder is made ofliquid silicone rubber.
 10. The mist generator device of claim 9,wherein the liquid silicone rubber has a Shore A 60 hardness.
 11. Themist generator device of claim 8, wherein the capillary aperture is anelongate slot having a width of 0.2 mm to 0.4 mm.
 12. The mist generatordevice of claim 1, wherein the capillary element is generally planarwith the first portion having a generally rectangular shape and thesecond portion having a partly circular in shape.
 13. The mist generatordevice of claim 12, wherein the capillary element has a thickness ofsubstantially 0.28 mm.
 14. The mist generator device of claim 1, whereinthe capillary element comprises a first part and a second part which aresuperimposed on one another such that the capillary element has twolayers.
 15. The mist generator device of claim 1, wherein the mistgenerator device further comprises: at least one absorbent materialwhich is provided adjacent the mist outlet port to absorb liquid at themist outlet port.
 16. The mist generator device of claim 1, wherein theplane of the atomization surface is substantially parallel with alongitudinal length of the mist generator housing.
 17. The mistgenerator device of claim 1, wherein the ultrasonic transducer iscircular and has a diameter of substantially 16 mm.
 18. The mistgenerator device of claim 1, wherein the liquid chamber contains aliquid having a liquid viscosity between 1.05 Pa·s and 1.412 Pa·s and aliquid density between 1.1 g/ml and 1.3 g/ml.
 19. The mist generatordevice of claim 1, wherein the mist generator device further comprises:an identification arrangement which is provided with the mist generatorhousing to identify the mist generator device, the identificationarrangement comprising: a one-time time programmable integrated circuit(OTP IC) having a memory which stores a unique identifier for the mistgenerator device the one-time programmable integrated circuit (OTP IC)comprising a digital core which includes a cryptographic authenticator;and an electrical connection which provides an electronic interface forcommunication with the one-time programmable integrated circuit (OTP IC)and the driver device.
 20. The mist generator device of claim 19,wherein the memory of the one-time programmable integrated circuit (OTPIC) stores a record of a state of the mist generator device which isindicative of at least one of a historic use of the mist generatordevice and a volume of the liquid within the liquid chamber.